Below is a brief (yet incomplete) list of open source and free software projects where I am involved or to which I have contributed a significant amount of code. You might also want to check my GitHub and ohloh pages.
The ocaml-arm project provides a new ARM backend for the OCaml native code compiler, which fixes various bugs and shortcomings of the previous backend and includes support for both armel and armhf targets (currently limited to Linux).
The ocamlnat project provides a new native code toplevel for the OCaml language, which is mostly compatible to the byte code toplevel, but up to 100 times faster. It is based on the optimizing native code compiler, the native runtime and and earlier prototype by Alain Frisch. It is build upon Just-In-Time techniques and currently supports Unix-like systems running x86 or x86-64 processors.
The ocaml-experimental project serves as a playground for
experimenting with new features and changes to the OCaml
language and runtime, including a new native code toplevel
ocamlnat, which has since been moved to the ocamlnat project,
and an implementation of the linear scan register allocator for the optimizing native code compiler
With PhotoAccess you can easily transfer photos directly from your iPhone, iPad or iPod touch to any computer using a web browser over WiFi. Select an existing photo or take a new picture, and PhotoAccess will display a download URL below the photo. Enter that URL in a web browser on any computer on the same network and you can download the full resolution photo, rotated to the correct orientation. The perfect solution to transfer just that one photo which you need right now.
BMKit is a collection of various useful Objective-C classes and categories for iOS (and Mac) development. It is always work-in-progress as I constantly add new features as needed. BMKit is designed to be embedded into other Xcode projects, see the project website for details.
With iFlashLight+ you can turn your smart phone into a flash light using the LED light on the iPhone 4. The camera LED flash on the iPhone 4 is mega bright and when turned on in a constant stream, it is unrivaled in terms of lighting power.
I wrote iFlashLight+ when I received my brand new iPhone 4 and discovered that all available iPhone 4 LED flash light apps sucked for some reason (ads, malware, crashes, etc.). iFlashLight+ is free and open source, and - unlike other flash light apps - comes without ads and malware.
git-hooks provides a simple mechanism to manage hooks for several Git repositories in a unified and simple way. It allows you to install hook scripts in a central location and use them for your Git repositories.
git-utils is a collection of simple utilities that made my Git life easier in some way or another. I tried to clean them up as much as necessary prior to putting here, so it should be easy to use for others as well.
Thunar is a project I started in mid 2004 (initially named Filer, but renamed to Thunar, because of a name clash with Jens' Perl Filer), which aims at developing an easy to use, lightweight file manager for the Unix/Linux desktop (specifically the Xfce Desktop Environment).
The Thunar Archive Plugin is a very simple plugin for the Thunar file manager, which
allows users to create and extract archive files (i.e.
.zip files) from within Thunar, using the context menu.
Over the last years I wrote various bits and pieces of the Xfce desktop environment. I developed and maintained various core parts of the Xfce desktop environment, including the new file manager Thunar, which I wrote from scratch to replace the unpopular Xffm file manager, the Session Manager, the Xfce Libraries, the Terminal, innumerable plugins and goodies, and several other core components.
The Xfce developer tools provide a collection of scripts and M4 macros that are required to build the Xfce core desktop components and various other software packages straight from SVN/CVS. You do not need the developer tools if you are building from the release tarballs.
The UPiDiff tool was developed as part of a hands-on training at the University of Siegen back in 2003. It was renamed since then and is now known as SiDiff. Its constantly extended with new features every year, but unfortunately it's one of those University projects that doesn't attract external developers because there's no real way to get involved.
The TPML tool was developed as part of an university project at the University of Siegen from 2005 to 2009. Its purpose is to help students understand the semantics of programming languages and the related type theory.