There are some other projects in which I have collaborated (or at least I tried to), but I haven't been collaborating for a while:

• Apache Jakarta Commons Configuration: Library for Java developer which offers advanced features for reading properties files or access XML files as if it where properties files. I've sent several patches which have been kindly accepted.
• GNOME Hispano (Spanish): Group of people dedicated to promoting GNOME within the spanish speaking community. I was the webmaster and helped convert from a static website to a dynamic website based on XML + XSLT.
• GNOME DB: This project lead by Rodrigo Moya has developed very nice libraries and tools to help develop applications who need to access different types of datasources (from XML to relational dbs). I helped as the webmaster but never had the time to help with the C code.