I like Delicious. My experience so far is that it's easy to use. I had no problem signing up and importing bookmarks. I just went through in about 5 minutes and edited all of my bookmarks by adding tags. I also really like that on this site, just like other social sites, you have the option to keep some of your data private and only publicize certain parts of your profile. I have opted to share some of my links for the purpose of this thing. They are not library related, but more fun in nature (these are different sites I visit when I'm not working, but not all the sites I visit when not working). Enjoy!