I'm admittedly biased, and probably going to get downvoted for self-promotion, but check out our product, AgileZen. We launched last year and were acquired by Rally Software at the end of March. Too much project management software isn't geared towards small teams, and we've tried hard to fix that. http://agilezen.com/
Upvoted because I like the look of the software. However, I feel strongly about being able to try out collaboration software with > 1 person before paying for it. Not looking for a free ride, but I don't think it makes any sense to "test" out a team mgmt/communication software by myself. That's why I use Acunote.
