These days, even a mid-range Android device packs enough processing power to handle most productivity tasks – from managing email and tasks to drafting articles and coding. Of course, this process requires that you have the appropriate apps installed on your Android device, but plenty of high-quality open source apps are at your disposal. In this article, I'll cover several excellent open source apps that can transform an Android device into a powerful and versatile productivity machine.

System Tools

Most virtual keyboards for Android are optimized for fast and efficient text input at the expense of certain features. Some keyboards, for example, do away with the Tab key, which is essential for working in the terminal. Other keyboards lack dedicated arrow keys, making it difficult to select text and move the cursor. Additionally, almost none of the available keyboards have dedicated function keys.

Enter Hacker's Keyboard [1], a keyboard replacement that replicates the regular keyboard layout, so it is perfectly suited for users who depend on the arrow, Tab, Esc, and other keys in their daily computing. Better still, Hacker's Keyboard features the Fn key, which evokes a separate layout containing a numerical keyboard and a function keypad.

Hacker's Keyboard can also handle multiple keyboard layouts, and you can easily switch between them by swiping on the Space key. The keyboard supports word completion functionality, and completion dictionaries are available for several languages (the English dictionary is included by default). Hacker's Keyboard also has a dedicated configuration interface that lets you enable the keyboard, install additional completion dictionaries, and tweak the keyboard's options (Figure 1).

Figure 1: Hacker's Keyboard lets you enable and configure the keyboard.

An Android device without a proper file manager is as useful as a square wheel. Fortunately, you have several open source file managers to choose from, including OpenExplorer and Ghost Commander. OpenExplorer [2] sports a sleek interface that works well on practically any screen, and the file manager packs a raft of useful features (Figure 2). OpenExplorer can handle remote servers, and the file manager supports the popular FTP, SFTP and Samba protocols (Figure 3). Better still, OpenExplorer also supports cloud storage services, including Box, Dropbox, and Google Drive.

Figure 2: OpenExplorer is a capable file manager that packs a wide range of useful features.

Figure 3: OpenExplorer supports popular protocols and cloud storage services.

The ability to handle remote servers is only one of OpenExplorer's many talents. The file manager also comes with a built-in text editor that lets you view and modify text files. On rooted Android devices, the file manager provides read/write to system directories, and the app lets you browse and extract archives in popular formats, including ZIP, TAR, TRGZIP, TBZIP2, and 7ZIP. The Favorites feature in OpenExplorer lets you bookmark often-used folders for faster access. Finally, the file manager supports so-called smart folders that offer convenient access to pictures, videos, music, and downloads.

OpenExplorer is a competent file manager, but if you prefer the efficiency of a twin-panel file manager, then Ghost Commander [3] is right up your alley (Figure 4). Ghost Commander's twin-panel interface makes it supremely easy to work with files, and numeric shortcuts let you perform common operations with a single key press (handy if you use a physical keyboard with your Android device). Ghost Commander can handle the FTP protocol right out of the box, but you can add support for Samba and SFTP by installing optional plugins. Similar to OpenExplorer, Ghost Commander gives you read/write access to system folders on rooted Android devices, and the file manager's Favorites feature can come in handy for bookmarking frequently used directories.

Figure 4: Ghost Explorer's twin-panel interface makes it easy to work with files and directories.

KeePass is a great tool for storing and managing passwords on the Linux desktop, and KeePassDroid [4] makes a perfect companion to it (Figure 5). Using this app, you can use a KeePass password database on an Android device. The app can open existing databases in both older KDB and newer KDBX formats, and you can use the app to create new databases (in the KDB format only, though).

Figure 5: KeePassDroid is a useful app for managing passwords on Android.

Like the desktop application, KeePassDroid can handle databases protected with a key file. When you open a database record in KeePassDroid, the app conveniently copies the username and password to the clipboard, making it easier to insert the login data into a web form. More importantly, the app automatically clears the clipboard after a specified period of time for better security.

Task Managers and Note-Taking Apps

Task managers and note-taking tools are productivity staples on any platform, and Android is no exception. When it comes to task and to-do managers, you can choose from several apps. The simpleDeadlines app [5], for example, is a task management app for users who value simplicity. As the name implies, the app is particularly suited for keeping tabs on deadlines, so it can be an indispensable tool for anyone dealing with deadlines on a daily basis (Figure 6).

Figure 6: SimpleDeadlines is a no-frills app for keeping tabs on deadlines.

SimpleDeadlines is, indeed, simple. It lets you create tasks, assign due dates to them, and arrange created tasks in groups. The app assigns a color code to each task based on its deadline's proximity. For example, all overdue and upcoming deadlines have the red color label, looming deadlines are marked with orange, and so on. On each boot, simpleDeadlines displays a notification containing deadline counts for each color code. SimpleDeadlines also works with the DashClock Widget app [6], which lets you view deadlines in the lock screen.

If you are looking for something more advanced than simpleDeadlines, then you might want to give NoNonsense NotePad [7] a try. This hybrid app combines task management and note-taking functionality wrapped in a sleek and user-friendly interface (Figure 7). You can organize notes into lists, and you can turn a note into a task by assigning a deadline and reminder to it. Although you can't assign a priority to the tasks, you can rearrange them by dragging them up and down.

Figure 7: NoNonsense NotePad can handle notes and tasks.

In addition to regular time reminders, NoNonsense NotePad also supports location-based reminders that trigger notifications when you are at a specific location. The app continuously saves new and modified notes, and it offers the clever Time machine feature, which lets you view all previous versions of a specific note. More importantly, NotePad supports syncing via the Google Tasks service, so you can keep notes and tasks in sync between multiple devices and platforms.

Managing Email, Reading, and Writing

When it comes to picking an email client for use with your Android device, you can do much worse than installing K-9 Mail [8]. Indeed, this must be one of the most powerful yet user-friendly apps on the Android platform. K-9 Mail supports multiple email accounts, and the account setup assistant makes the process of adding accounts very straightforward (Figure 8). The assistant supports popular email services like Gmail, Yahoo! Mail, and FastMail, so if you have an account with any of these services, you can add it to K-9 Mail in a matter of seconds. Provide your email address and password, and the app takes care of the rest.

Figure 8: K-9 Mail is probably the most powerful and versatile email client for Android.

K-9 Mail features the Unified Inbox, which lets you manage incoming email from all accounts in one place. The app's interface borrows some ideas from the Gmail app, including the ability to view email as conversation threads. The commands in the context menu let you process email quickly and efficiently: long-tap an email item, and you can reply to the email, forward it, mark it as unread, move it to another folder, and so on. The useful More from this sender command displays all recent email messages from the sender. K-9 Mail supports multiple identities, too, which can come in handy for use with email aliases. Other de rigueur features like attachments, signatures, searching and sorting capabilities, and other creature comforts are present and accounted for.

An ebook reader, such as the FBReader app [9], is another useful addition to your productivity quiver. This app supports several popular ebook formats, including EPUB, MOBI, FB2, and TXT. The app provides direct access to several online ebook catalogs (e.g., Smashwords and FeedBooks), so you can browse, purchase, and download ebooks directly from within the reader. You can add custom catalogs, too, and this feature can be useful for wirelessly transferring ebooks [10] from the Calibre ebook suite.

Thanks to a wide range of configurable options, FBReader is infinitely customizable (Figure 9). You can tweak practically every aspect of the app: from fonts (the app can use any TrueType font) and themes, to line spacing and page-flipping effects. Of course, the app features the usual creature comforts, like searching and bookmarks. You can bookmark an entire page or a text selection, so you can use the bookmarking feature to save text snippets. FBReader also lets you perform other actions on the currently selected text using a pop-up menu. You can highlight the selection by applying a color to it, and you can share the selected snippet via Android's sharing feature.

Figure 9: FBReader is an infinitely customizable ebook reader, and it supports several ebook formats.

Your productivity toolbox would be incomplete without a text editor, and if you are looking for a text editor that can be used for both editing and coding, then 920 Text Editor [11] is just the app you need (Figure 10). It supports syntax highlighting for many popular programming languages, including Java, JavaScript, Perl, PHP, Python, Bash, and many others. The editor can also handle a wide range of encodings, and it packs a lot of useful features: from search and replace functionality to autoindent and support for multiple tabs.

Figure 10: 920 Text Editor is good for both writing and coding.