I like the groups on myspace, facebook and yuwie. That way you can target your market. It's a fine line not to spam though. There are also Yahoo, Google and Msn Groups. Or, you can start your own.
Thats so true, especially in the myspace forums and groups, it seems to be mostly spam. But I went on to create my own group in myspace so that I can control the type of content that I want there and find that is much better. It is always important to know who and where your target market is, so you are right on with that. Once you know where your target market is, there is no need to spam or really advertise. Just build relationships with those people and brand yourself online.