I took a few hours recently to set my Eee PC 701 2G Surf up as a dedicated emulator machine. I picked up a dirt-cheap 16GB Sandisk Cruzer USB stick for $9 and downloaded an ISO of Mandriva Linux 2011.0.
This thing is pretty sweet! It runs SNES, NES, Game Boy, Game Boy Color, Game Boy Advance, Nintendo DS, Genesis, MAME, and Sega Master System emulators. Pretty much anything 2D it can handle easily.
Even better, I had a bunch of space left over on the USB stick for mp3s and oggs, so I can listen to some decent music while I’m driving in my car thanks to the audio input jack on my car stereo.