I use the GMARKS extension. Not sure on FF3 compatibility but it’s updated regularly and places copies of your bookmarks into Google as well as locally. You can tag and search your bookmarks also.

I had tried the google extension and found it lost bookmarks for me occasionally, GMARKs has been fine for over a year of usage now (although saying that I think I might export my bookmarks someone safe just in case).

The Lifehacker post does have some good news though, that the Google Toolbar will be continuing. However, it is still not available for the Firefox 3 beta.

I tested Weave and so far it works fine. Foxmark works fine too but it’s just the bookmarks.

Use Foxmarks, absolutely the best solution out there. As mentioned above, in addition to syncing all your bookmarks, it also makes them available online incase you aren’t near your own computer.

If all you need is bookmark syncing, FoxMarks is the way to go. Not only does it sync bookmarks, it also includes the associated “favicons” and even makes all your bookmarks available in your FoxMarks account from any browser in case you’re using a computer without Firefox or where you can’t (or shouldn’t) install add-ons. http://www.foxmarks.com/

There’s “Weave” out there as replacement from Mozilla, even though it is a beta still…

Well, it’s not Firefox (and even myself, a diehard Opera fan, have to admit FF3 is an incredible browser) but Opera 9.5 does have syncing for most things Opera… or at least any number of desktop machines and Opera Mini, for now.

Wow! This is a real bad news! I do not care if I lose all my other extensions but not that one!