You can also find forums related to your site, (search - %keyphrase% forums) and put your link in your sig. You really don't even need to post since the link can be found in your profile. It'd probably help a bit more if you did actually make a useful post or two on each one that you find. I found a bunch for one topic. I figured I'd join maybe the top 10 or 15 and see how much it helps me in the serps.
That is on this weeks to do list.
