Teamspeak 3 server would be premium. I've done alpha testing for many games, and a TS always helps. Great for real-time developer feedback as well. I've been moderating a server for an indie developer over 3 years now. It's really useful to have knowledgeable folk on voice chat for any new players that have questions. Speeds up theory-crafting a lot. Also a steam group is a good idea as well.