Someone said to us recently, "Space is the new time." At TNM, technology allows us to have the constraints of geography pretty well in hand.
We use Skype and bridgelines for conversation, Wikis for creation, Backpack and Basecamp for administrative and organizational tasks, email for many things. We're constantly testing new processes and tools and have a reliable, simple system right now. All participation is voluntary, so people almost always show up.
We have never all met in person, though small groups convene from time to time. We co-lead courses sometimes. It's great fun to show up at a course venue and meet someone you've worked with for years and never seen face-to-face!