You're probably still waiting for Amazon to ship you your pre-ordered PS3 slim, however while you do, the chaps over at iFixit have already taken one apart to see how Sony managed to get it so small.
A massive 95mm diameter fan with a whopping 17 blades plus a large piece of custom molded plastic to route air from the fan over the heatsink.
Elsewhere the "teardown" as ifixit likes to call them (it does this on a full time basis) found that most of the space is taken up by a desktop PC sized Blu-ray drive.
Other geek stats to impress your mates with down the pub? Sony has stuck with a lot of the same chip manufacturers as the original PlayStation 3 and that upgraded 120 GB drive is a Toshiba-manufactured, 5400 RPM standard notebook SATA drive.
More pictures and a blow-by-blow account in 27 steps over at ifixit (via read link below).