I just signed up my small business on the new small business social network: http://www.littleengine.com/ Do you think this will help out, in terms of SEO juice? They just got mentioned on a bunch of big time web2.0 sites, and it's free.
What is the PR value of this site? If it has a very high PR and allows you to create a regular crawlable link, it may pass some SEO juice, if any. But my bet is that even if it does, the effect is very minimal. Depending on what business you are in, if you can find a forum site like this for your line of business, you may get a boost of your site by creating a link there. Whether you get a boost or not has a lot to do with the link site content. If you create a link at a site that sells DVD for your web design company, that link is pretty worthless.