There are SEO tools that let you piggyback off your competitor's link building activity like the one implemented at work that is called www.analyticsseo.com
Then you also have the traditional PR way...social networks, directories and places and online interactive campaigns ( Youtube is a great hub).
The best free backlinks are articles, forum posts, blog comment and profile links. Just stick to these and you should be able to rank up in less then 3 months.
Bookmarking is one of the easiest way of getting the traffic Free advertisement is something non-relevant backlink arising So i suggest not to go through this.
Many ways to build a link to your site by
directory submissions, Social bookmarking, forum posting, blog posting and comments posting, press release etc...