Fast depth of field

Are there any tricks for getting a depth of field effect other than using the accumulation buffer to jitter the image.I’m looking for a solution that is relatively fast,but it doesn’t have to be really speedy.I’ve been looking at Ridge Racer 5 on the PS2,and it’s DOF effects are really smooth.

Check this out:

Couple that with hardware accelerated mipmap generation and it should be pretty fast