I experimented with Delicious earlier this year and found it first, to be a great way to organize and access my own bookmarks. With further experimentation, I see how I can generate bookmarks to share with classroom teachers from delicious rather than copy and pasteing them into an email. Hopefully this will encourage them to explore delicious as well and begin to use it with collegues as well as students. I am at an elementary school, so there is not a huge amount of internet use for projects going on, but with our TEKS being more involved with research this year, this may be in higher demand.
I checked out the other sights mentioned and may use some as well, but I feel Delicious will be of most benefit for me.