KRDC is a client application that allows you to view or even control the desktop session on another machine that is running a compatible (RDP/VNC) server.

Roundup is a simple-to-use and install issue tracking system with command-line, Web, and e- mail interfaces. It manages a number of issues (with flexible properties such as "description", "priority", and so on) and provides the ability to (a) submit new issues, (b) find and edit existing issues, and (c) discuss issues with other participants. The system will facilitate communication among the participants by managing discussions, and notifying interested parties when issues are edited....

Key features of i3 are correct implementation of Xinerama (workspaces are
assigned to virtual screens, i3 does the right thing when attaching new monitors), XrandR support (not done yet), horizontal and vertical columns (think of a table) in tiling. Also, special focus is on writing clean, readable and well documented code. i3 uses xcb for asynchronous communication with X11, and has several measures to be very fast....

EMMA is a fast Java code coverage tool based on bytecode instrumentation. It differs from the existing tools by enabling coverage profiling on large scale enterprise software projects with simultaneous emphasis on fast individual development.

CL-PPCRE is a portable regular expression library for Common Lisp.,

The Python Imaging Library (PIL) adds image processing capabilities to your Python interpreter. This library supports many file formats, and provides powerful image processing and graphics capabilities.

Crystal Space is a free, cross-platform software development kit for realtime 3D graphics.
It supports Windows, Linux, MaxOS/X and more. Though written in C++, other languages like Python can also be used to write programs.
Based on a plugin system it's very modular and extended easily. ...

gitg is a git repository viewer targeting gtk+/GNOME. One of its main objectives is to provide a more unified user experience for git frontends across multiple desktops. It does this not be writing a cross-platform application, but by close collaboration with similar clients for other operating systems (like GitX for OS X)....

ICQ-like Eclipse Plugin, programmers can chat with each other under the Perspective of Eclipse

Small, secure dns cache and resolver written by Daniel J. Bernstein, the author of qmail. djbdns is extremely fast, very secure and easy to configure (think 'opposite of bind zone files').