What about Delicious? I've been using it for over 4 years now and love it. I'd be lost without it.
Aside from having my bookmarks accessible from any browser, any computer I use, I'm in love with the Delicious Bookmarks Toolbar. I use different tags to organize what I want on the toolbar. For example, I have "toolbar:support" (links to our 3rd party support services), "toolbar:company" (our company links), "toolbar:companyit" (links to our IT pages), "favorites" ("company" is replaced by our company name, but anyways...). I chose those tags to be listed on the toolbar. Then I click on the tag drop down and it will show all of the links tagged with that tag. I have different tags that I have displayed on the toolbar at home vs. my work laptop.
Delicious
http://www.delicious.com/
Quick Tour of Firefox Add-On on Delicious
http://www.delicious.com/help/quicktour/firefox
Quick Tour of Internet Explorer on Delicious
http://www.delicious.com/help/quicktour/ie
I had looked at Xmarks when it came out but I was skeptical of how they could provide a service like this for nothing. I honestly wasn't aware they were still around. I was hopeful for Google Bookmarks but it never turned into something useful like Xmark or Delicious. I feel much more comfortable using Delicious since they're owned by Yahoo. Granted, Yahoo could pull the plug, but I don't see that happening.
