If you're looking for a game emulator to take around with you, you might want to check out Ben Heck's latest project. While it's not actually his creation, he did design the case and give it a name.
The Gameport currently can play Atari 2600 games and Colecovision cores, though it will likely support other systems in the future with software upgrades. You'll be able to load up games via USB and take it on the go. The memory is only limited to the size of the SD card you use.
No word yet when these will be made available to the public or how much we'll have to fork over for one.
Port your games around with the Gameport [via benheck]