Matt Cutts of Google talking about the value, (or not), of directory links, and why Yahoo`s passes their test.

What types of directories are seen as sources of paid links?

http://www.youtube.com/watch?v=1Pu1YWcIh04

I still find that I'm getting good results with directory listings. It doesn't work for all niches but for service based industries like car hire it still works a treat.

I Just checked and it's proven that links on digg are dofollow. Making a bookmark on digg will certain add value to your site.