I wasted a lot of time thinking about some wise solution for online synchronization between my mailboxes and bookmarks at home, work and multiple remote locations.
Finally I got tired of it - and, urged by gholam, just bought this:
Put on it portable Firefox. Put on it portable Thunderbird. Imported 1,5 GB of my mail archives. Consolidated bookmarks files. Cleared some crap out of them all in process.
And it works. The best of it - I don't need to care about sync. anymore. Because there are no sync needed. And backups become very easy - just copy paste content of disk on key to hard disk and bingo.
Note: if you do the same - choose quickest possible flash drive. When I edit bookmarks the small delay is here.