I’m not a graphic designer, and if I want to convince participating projects to include my logo in their program to advertise this site, I have to come up with something a little better.
So, beat me (with a better logo). Good luck! The winner will get an honorary mention on this site.
This is my attempt. The LaTeX source is available, but it requires the Lucida font set. An α-channel is added to blend the edges on coloured backgrounds, but this is rather trivial to add yourself.