This Guy really get hot .. I have it setting on my desk by the speakers on both side and under the computer by the display these area are very hot to touch...
I put my modern notebooks atop a wire dishrack to provide enough clearance to allow air to circulate. Make sure it's rubber coated rather than plastic so the Mac doesn't slide around too much.
Kensington makes this nice USB fan if you'd like to chill the thing further.