I used to feel that GenForum's posters were more deeply involved in research, but the amount of posting here seems to be fading - lack of promotion of the site I suppose.
You do not have to "join" Ancestry to post to their freequery boards.
Don't forget about the shared email lists hosted by Rootsweb. They are easy and free to join simply by sending an email for example to email@example.com with only the word SUBSCRIBE in the subject.
Some good email lists are also hosted by yahoo-groups, but they are a harder to find.