Blinklist
I have played a bit with some social bookmarking websites, but have never been terribly impressed. I just signed up for Blinklist however, and I think it may be worthwhile. What impresses me is that you can query for any tag, and your query will have an RSS feed. I notice that if you click on the rss feed, it gives you javascript code so that you can append your links right into any webpage. I am sure this will be very useful. I am not positive why.
Funny how I linked to them, and a few seconds later their website went down.
Lets just call it the "Fingertoe effect"