Raspberry Pi is right now in Alpha Board stage. The board is much bigger than what they are planning for release. Though it seems they changed they size format. They want it now to be around the size of a credit card.
The device is suppose to run an ARM version of Ubuntu and it has a nice GPU. The CPU is said to be less powerful than the one in Pandora so getting N64 emulator to run nicely might require some more work. Of course all emulators need to be ported first, but it shouldn't be too hard in case of C and C++ ones. There are lots of ARM ASM based emus too, but those probably would need more work too. Its all doable, so it makes the Raspberry Pi a good product (for its price). In fact for that price its an excellent product.