I have been mostly utilizing 2 methods: social bookmarking such as Digg, Delicious, Diigo, Mixx... and also commenting on higher-PR blogs in a similar niche as me. However, what other methods of linkbuilding are there aside from social bookmarking and commenting?
Profile-based links are also good. As long as they are DO FOLLOW and have Page Rank on the main page.
I also do use profile links on my different social network profiles (Digg, Stumble). I find that link directories don't really help much, as I have tried those before. Link exchanging is a really good idea though, haven't tried that tactic but heard good results from it.
Just to tag on to what other people have said - directory submissions, when done right are awesome. directory submissions - if it's free, make your own list. those autosubmission software don't work as well compared to doing it manually. Switch up anchor text, description for maximum results Yahoo dir - awesome stuff. I get it for all my main sites. There are other paid dirs (joeant, botw (this one I don't recommend), business) that offer nice high PR links back. Search your competitors and see what they got. PRweb - get the $300 one. And, don't forget your best friend: http://backlinkwatch.com/ Go steal your competitors backlinks. Clone your competitors' links and you'll be ahead of them fast.