Cohousing-L is an Email-based list about cohousing started in late 1992. The list volume (# of messages/day) varies quite a bit, but you can change your subscription to the digest version if the "send every message" mode is overwhelming. All of the sent messages (over 34,000 messages as of Dec 2011) are archived and searchable - which is an excellent way to learn about many issues involved in creating and living in cohousing.
Many of the best-known people in the Cohousing world participate in this dialog on a day-to-day basis, including several Cohousing consultants, Cohousing developers, Cohousing architects, and Cohousing activists.
Cohousing-L is loosely affiliated with Coho/US.