Contrary to popular belief, many of these social sites are populated by people an average age of 35 who are 20% more likely to spend money online than people who come from a natural Google search. So yea, you can do some good.You need to "Sell without selling". Pretty much provide a whole lot of content your target audience will love and point the way to your sales page.You'll also want to use a few other places

igg, Facebook, Squidoo, Blogger... just check for lists of web 2.0 sites and you'll do just fine.