Apple's site has the spec as well. 3GB. I just happened to have looked up the RAM specs for an iMac of the time and it has the same limitations. I also recall the hoopla at the time, not only from Mac users, about systems topping out at 3GB instead of 4.

Matt, don't forget to check out that bundle I mentioned at MacUpdate. Still over a week left on it and you'll get a bunch of software, including VMWare for $50.