This isn't supposed to be possible, but Ben Englert reports to me that you can actually use two displays from a Mac mini. It's a bit of a hack, but Matrox's DualHead2Go takes the mini's DVI output and splits it into two VGA signals.
Then you need to use SwitchResX or modify some preference files yourself, and the mini thinks it has one reaaaaalllly wide monitor. That means it doesn't behave like two displays normally would—you get a single menu bar across both screens, splash screens pop up in in the middle of both displays, and you really should have two identical-height monitors, since you have no way to arrange how they relate to one another in the Displays preferences—but it's a pretty neat hack nevertheless. Not for everyone, but possible.