Konttori, posting on the Thoughts (Nokia Internet Tablet Development) Blog, shared a video (embedded below) showing a SNES emulator (DrNokSnes) running on the Nokia N900. The video also includes a demo of controlling the SNES via Nintendo Wiimote controller (over Bluetooth) and using the TV-Out functionality to play on a big screen. It's a nice example of the flexibility and power sitting underneath the first Maemo 5 device.
Here's the video: