A free little iChat extension called Chax just released a version that allows for tabbed iChat windows. They did a very nice job.
[robg adds: Chax is a previous Pick of the Week winner, but it didn't have tabbed window support at that time. This feature has been long-requested, so I felt it worth a new mention as a standalone hint. I've been using it for a week or so now, and it's pretty well done. I would, however, prefer that the tabs went vertically, as you have to make your chat window pretty wide to actually see names on the tabs. Other than that, though, it's a handy way to consolidate window clutter.
And yes, other third-party chat clients have had tabs for a while now. Unfortunately, file and image transfer don't work well with those clients, and as such, I can't really use them...]

