Currently Unity support’s Android, iOS, Mac, Linux, PC, PS3, XBox and Wii. The options in italics are paid for options that you would have to buy an extension license from Unity in order to have access too, however the price you pay will be trumped with the amount of time / effort you save during development cycles thanks to the truly cross-platform nature of Unity.
At the time of writing Unity Pro costs $1500 and allows access to a whole host of useful features listed here. However if you don’t want to pay to use the Pro version you can currently download Unity for free and without restrictions so long as you don’t need any of the aforementioned features.
The bolt-on licenses for iOS, Android and Flash player are either $400 each for the non-Pro version and $1500 for the Pro version each.