Which one do you think is the best social bookmarking tool?
There are so many of those availabe for everyone for free and from what wee can see, if used intelligently they can bring huge waves of traffic to your site.
Some of the top social bookmarking sites are digg, Yahoo! Buzz, StumbleUpon, reddit, Technorati, del.icio.us, kaboodle, mixx, Propeller, newsvine.

Which one have you used and have given you the best result?
Also if you can tell the pros and cons of using them and which one is the most user friendly of them then it will be great.