Sync Mail Dir is a set of utilities to synchronize a pair of mailboxes in Maildir format using SSH to transfer data. It provides the smd-pull utility to pull changes made on the remote mailbox, smd-push to propagate local changes to the remote mailbox, and smd-loop to iterate push and pull in a timely way. Unlike OfflineIMAP It requires no IMAP server to be installed on the remote host. Moreover, it never attempts to automatically resolve conflicts between incompatible mailbox statuses; it just notifies the user explaining how he can fix the problem. Its design is similar to that of Maildirsync, but it is more efficient in terms of CPU cycles and disk I/O.
Listaller unifies the way you manage software on your Linux system by providing a user-friendly, application-centered software manager GUI. It also provides a software setup package format (the IPK package format), which works on all Linux distributions, as well as tools to make your application binaries work on every Linux distribution. The project has merged with Autopackage some time ago. One of Listaller's strengths is its close integration with AppStream and PackageKit. This means that you will be able to manage Listaller-installed applications with your favorite package-manager, like GNOME-PackageKit, Apper, or even the Ubuntu Software Center. Listaller is primarily designed to be run on Linux distributions, but it could be ported to *BSD.
Déjà Dup is a simple backup tool. It hides the complexity of doing backups the 'right way' (encrypted, off-site, and regularly) and uses duplicity as the backend. It features upport for local or remote backup locations, including Amazon S3. It securely encrypts and compresses your data. It incrementally backs up, letting you restore from any particular backup. It schedules regular backups, and integrates well into your GNOME desktop.
Ejecter is a little tool that makes it possible to unmount external devices and eject CD-ROMs without having to right-click on the device icon (either on the desktop or in Nautilus). It sits in the background and shows an icon in the system tray when one or more peripherals are connected to your PC: once clicked, a window appears with the list of the devices (volume name and device type, and much clearer than the similar thing available on Windows) and the related eject button. Being written in Vala, it is translated into C code and then compiled. This means that it's lightweight and consumes little memory, does not require a full VM like Python, and has no strange requirements to run (just GLib/GTK).
DeaDBeeF is an audio player for GNU/Linux and other UNIX-like systems. It is written in C with some plugins in C++. It has minimal dependencies, a native GTK2 GUI, cuesheet support, support for MP3, Ogg, FLAC, and APE, chiptune formats with subtunes, song-length databases, and more. It is very fast and lightweight, and extensible using plugins (DSP, GUI, output, input, etc.). The GUI looks similar to Foobar2000.