Nintendo:

SEGA:

A new trick has been found over at PS3hax that allows SNES and Gensis Emulators to run.  I don’t know about the quality or safety of running this but it seems easy and pretty safe as well.  Check it out after the link.  Note that it mentions your PS3 must be PS2 capable.  The 80gb has not be tested yet.

PS3 Emulators: It Has Begun!