I have done some experiment yesterday and joined Google groups and submitted my site link with some description and with some title hope i will get god response from Google groups mine site is based on music download that's why i have submitted my site in category music .... do i get good traffic from Google group if i submit 100 posts per day or its just waste of time ....
find forums related your niche , be an active member and post links in the signature.Do not spam it will make a negative result