I have worked on a lot of open source projects in the last 15 or so years. Below you can find more about what I have been involved with. The most recent activities are at the top.
hs-tls is a TLS implementation in Haskell, written by Vincent Hanquez. I contributed support for client certificates.
disassembler is a disassembler for x86 and AMD64 machine code, written in Haskell.
harpy is a Haskell library for dynamic machine code generation.
cpuid is a Haskell library for accessing the cpuid instruction on x86-like processors.
Turtle a constraint-imperative-functional experimental programming language. I developed it as part of my Diploma Thesis.
Mediocre is a small, Emacs-like text editor for the console which ran both on Linux and Solaris. It had multi-buffer and multi-window support, had basic syntax highlighting and was scriptable. You can download it here: mediocre-0.1.4.tar.gz
Sizzle is a Scheme implementation. This was done just for fun, but turned out to be a pretty complete implementation of R5RS Scheme.
wimpwm is a window manager for the X Window System. I wrote it because I wanted to use the same decent window manager both on my private Linux box and on the Solaris machines at University.
I have contributed to the GNU Guile project: I commited code, documentation and designed the Guile logo.