A broad (1"+) wood chisel can be used to pry the processor out of the socket, working slowly one side at a time. You don't hit it, you turn it like you might a screwdriver, and you keep it out at the edge just under the rim.

I have done several like this with no CPU fatalities. Presumably a knife could be used as well, but a chisel gives good control. (Mind you, I am a woodcarver, so am used to the actions involved.)

After the processor begins to come up, you can basically pull the rest of it up with your fingers. The pins are maybe 1/4" long, so you don't have much to pull.