Discussion board search engine?

I want to do some undercover research for various user groups of my company’s products. I’ve been searching for related discussion boards, to see what my users are interested in. Other than google, does anyone know of a search engine specifically for discussion forums? How about blogs?

http://technorati.com/ is one for blogs. there are quite a few other too, just cant remember the links.

also, check out Google Trends

R