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.
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.
gtkaml is an XML syntax and parser that extends the Vala.Parser and transforms all your tags into a valid Gtk+ UI class. It features a casual XML syntax for describing the way Gtk widgets are laid out in a (new) custom widget you're creating. Code "islands" (written in Vala) are used for widget signal handling and other methods/signals/properties that you're introducing. It doesn't depend on an external library at run-time, and it is much more readable than the usual UI boilerplate.
radare2 aims to create a complete, portable, multi-architecture, Unix-like toolchain for reverse engineering. It is composed of a hexadecimal editor (radare) with a wrapped I/O layer supporting multiple backends for local/remote files, debugger (OS X, BSD, Linux, W32), stream analyzer, assembler/disassembler (rasm) for x86, ARM, PPC, m68k, Java, MSIL, and SPARC, code analysis modules, and scripting facilities. It also has a bindiffer named radiff, base converter (rax), a shellcode development helper (rasc), a binary information extractor supporting PE, Mach0, ELF, class, etc. named rabin, and a block-based hash utility called rahash. Radare was rewritten as radare2, and the old version is only maintained for bugfixes.
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.