del.icio.us -- I had set up an account before arriving here and tried it out, but like so many other "things" -- it had been put aside without really using it.
I dumped all my bookmarks into it initially, so it really needs a good cleaning out, but I think it has potential. I've used the idea of bookmarks in a class, but not where students can add to them and they've always been static links, so seeing how other people use the resources has been interesting. Tagging is still the "new" aspect for me to remember to do when I save links -- and the visual clouds, like Wordle usually don't grab me as much, although it's probably just a lack of experience and practice with them.
Overall -- another tool to remember to use more with great benefits!