I've been submitting most of my blog entries to Digg and Netscape. What other ones should I consider?
its because the users that use digg never click on adsense because they know what adsense is and dont want you to earn cash from their clicks.
To find a good list, buy a social networking submission from the Services Section of this board and as soon as you get the report, you should see the best and popular social networks list
This may help: Type into google: Top 29 Social Media Sites that send traffic, from Tropical SEO Blog - I'm unable to submit links as I'm a new member
propeller, stumble , indianpad are good options, stumbleupon in particular has given crazy traffic for entertainment related posts