Google Browser Sync
Google Browser Sync for Firefox is an extension that continuously synchronizes your browser settings – including bookmarks, history, persistent cookies, and saved passwords – across your computers.
I've been needing something like this for ages ! At the moment I have to use my USB key to transfer saved password etc from my work laptop to my home pc, but the issue of security is still a big one. I don't save my on-line bank password anywhere so that'll be alright, but I do save various e-mail account passwords, the issue being that a google employee could hi-jack one of my accounts, ok you have to enter a PIN to encrypt the passwords, but I can't find anything that tells me how strong the encryption is! Humm I think a risk assessment is in order ;-)