[slantyyz]

Well, the system is open and hackable, I'm sure someone will write drivers to allow PS3, Wiimotes, 360 and generic USB controllers to be used.

[zdw]

PS3 and Wiimotes would be relatively easy, as both are just Bluetooth devices and the OUYA has that built in.

Xbox 360 controllers would require either wired or the RF adapter that MS sells for PC use.

[slantyyz]

Actually there are also dedicated PS3 USB and Xbox USB controllers, most commonly used in tournament fight sticks.