Works great for syncing address books in multiple copies of Firefox Rated 4 out of 5 stars
I switched to IMAP recently for my personal email and the IMAP works great for access from multiple computers, but I had a real problem with my address book since there was no easy way to make sure mutiple computers had the same address book. Sync Kolab does exactly that. All you do is create an IMAP folder in your own account to hold the sync info, then create a sync profile that specifies which address book you want to sync to that IMAP folder. Do the same in each computer and you then have perfectly synced contacts among multiple computers.
There are still a few wrinkles as it's still pre-release, but it works and the developer is quite responsive.