i am fairly good at seo but i have been only working on DIRS, BLOG posts, Buying Links from related sites and little bit of Article submission which by the way didn't work that well. my site is three years old and has a PR 3 but don't let it fool you because i get a good amount of traffic (3.5k/day) and it ranks well in google and yahoo. But what else is out there for link building and getting traffic??
I see you didnt mention social bookmarking sites. Have you submit your site to these kind of site ? Some say they have more weigth then dirs. As for getting more traffic, choose other keywords and optimise for different keywords.
Write about hot topics and matters related to your blog theme, you will get instant cache and good traffic also because of latest news/topic and fresh content if you write.
Write definitive articles on popular topics and promote them in blogs and forums. The content within those articles will drive ooooodles of long-tail traffic, and the links from forums and blog will turn into real links which will aid your site in general.
Forum signatures can only help you to get more traffics, but have no significant use in improving your page's PR.
Yeah that why i bought them...but to be honest they are not that good for getting traffic. well i am not seeing a good amount of traffic coming through them. and all my sigs are from big mostly related forums.