Native PlayStation 1
The PlayStation Store contains a section of "PSone Classics" games made for the original PlayStation console. These titles can be installed on the hard drive and played just as they were on the PS1, but you don't need to have the disc or install any additional software. They generally cost $5.99 and include some of the most popular titles, such as "Final Fantasy VII" and the "Crash Bandicoot" series.
SNES 9x
SNES 9x is an emulator compatible with a number of platforms, including Mac and Linux. If you install a Linux hack on your PS3, you can also run SNES 9x ROMs, files typically designated with an ".smc" extension. Because this type of software isn't native to the PlayStation 3, using it may void the console's warranty.
SCUMM VM
The SCUMM engine was created to run many classic point-and-click adventure games, such as the "Monkey Island" series. If you have used Jailbreak on your PS3 console, you can install a VM, or Virtual Machine, which runs the SCUMM engine. There are a number of titles available for this mod, some of which you can find in the Resources section.
GenesisPlus
The Sega Genesis was a well-known game console in its day, famous for the original "Sonic the Hedgehog" series. There is a version of this console emulator available for certain hacked PS3 systems, and many classic Sega games are available to play on it. Again, this hack voids the PS3 warranty.