The Team Chat Room

IRC (Internet Relay Chat) fills a nice gap between e-mail or message boards and a teleconference.  It's short and fast, like a real verbal conversation, but it keeps a log of what has been said so if you miss something, you can go back and read it. It alerts you when people mention your name (so you can be dragged into a conversation you may be ignoring).  It also makes a decent copy/paste between computers.

If you need something a little more long-form, such as what a team of programmers may need working on a complex bug, I also really like Google Wave, which is something like a mash up of IRC and a Wiki.

I recommend that any team of more than 2 people take the time to set up a team chat room.