Libgda is a (relatively small) database access library. It provides a wrapper like ODBC but with more features for accessing several database engines, a general data model for use with CSV or XML files, a metadata extractor that retrieves information about database objects in a common way, and a SQL console application (like mysql, psql or sqlite3 consoles).
AllTray is a program you can use on UNIX and UNIX-like systems, such as GNU/Linux or FreeBSD, running the X Window System. It is used to “dock” application software into the system tray (also known as the “notification area”). AllTray aims to be standards-compliant and work with any desktop environment/window manager+system tray combination that is also standards-compliant.
Epris is a D-Bus service and command line client to listen to music. Unlike xmms2 or mpd, it uses GStreamer and D-Bus. It supports all formats supported by GStreamer, and can play both video and audio. It supports gap-less playback thanks to playbin2. It has an extensible command line interface, a small memory footprint, automatic deactivation, and an easy D-Bus interface for other UIs.
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.
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.