I rave a fair bit about Ubiquity, but there are also a few other things from Mozilla labs that look promising. Last night I installed Weave on a couple of my computers, and am actually very impressed. Weave takes your Firefox history, bookmarks and tabs and syncs them across multiple machines. It worked flawlessly for me, and I would certainly recommend it to people who move between computers a lot.
I may have to try a couple of their other offerings, although I’m not exactly sure what all of them are meant to do.