Current projects:

I havn’t had time to actually write this section yet, so this is totally incomplete

GitHub profile - OpenHub profile

Since 2008 I am the lead developer of the ELKI Data Mining Toolkit.
ELKI Data Mining Toolkit

BPM tap toy, a tiny program to estimate the speed of a song, 2010

Google Summer of Code 2008
Google Summer of Code 2008 - Coordination for the Debian GNU/Linux project, 2008

Google Summer of Code
Google Summer of Code 2007 - Coordination for the Debian GNU/Linux project, 2007

MP3val GUI - a small user interface for the MP3 validator and repair utility “mp3val”, 2007

DBus-Inspector - a tool to introspect the DBus Message Bus for Linux Desktop developers, 2007

Kiss or Diss
Kiss or Diss - Voting on Videos from YouTube, similar to Hot or Not, but with videos, 2006

Google Summer of Code
Google Summer of Code 2006 - Mentor for the Debian GNU/Linux project, artificial intelligence for automatic classification of software packages, 2006

SSDDiff - semantic diff tool for XML files, 2004

mReplay
mReplay - sport replays on your mobile, project at Berkeley, 2005-2006

Pyroman - firewall configuration tool, 2005-ongoing

Debian SELinux - NSA Security Enhanced Linux integration for Debian, 2005-2007

LaySVN - a multi layer frontend to the subversion revision control system, 2005-2006

DebTags
Debtags - Debian package tags, a tool to easier lookup software packages, 2003-2006

Debian GNU/Linux
Debian GNU/Linux - free Linux distribution (software packaging, bug fixes, 1998-ongoing)

Prior to 2005:

Galeon
Galeon - Mozilla-basierter Webbrowser (Debian maintainance and patches, 2002-2005)

ISL3893 - Linux on the ISL3893 chipset based wireless access points (2003-2004)

ModLogAn
ModLogAn - logfile analysis tool (2001-2004)

Ming Library - flash library (2001-2002)

Bürgernetz München-Land
Bürgernetz München-Land - NPO for the public and regional use of the Internet (1998-2004)