I have some ideas for the Unnamed Semantic Web Client involving XBL that require various low-level changes in order to work.
So, I've been looking at some of the XBL code in Mozilla lately. There's a few bugs I'd want to see fixed and it would probably be simple enough to fix them myself. I think I understand the general architecture now to at least be able to say I know what I'm talking about. And Hyatt is offering a free dinner for helping him. (No link as all non-Safari related content seems to have disappeared from his Mozillazine-hosted site.)
If I could only get Mozilla to build properly, I might be able to do something.