I am a GNOME hacker and a member of the GNOME foundation. I am an Ubuntu member. I believe that the best way for me to contribute to open source software is to run Ubuntu on all on my computers and to use it every day. When I encounter a problem (which happens a lot) I report it. I try to fix it. I often succeed. Some problems are big and can't be fixed with patches alone -- you need to communicate the existence of a problem to other developers. That's exactly what I'm hoping to do with this talk.
I've attended several conferences but have never presented. I am, however, the proud owner of a red "I volunteered at GUADEC 2006" t-shirt. I recently participated (successfully) in Google's Summer of Code programme, creating a new library for writing panel applets. Code from this effort has made it as far up the stack as GdkPango -- again, through the principle of finding problems and fixing them.
This is my first proposal for a talk at a conference. Please be gentle. :)