My 3ghz P4 in my cramped room with my door shut runs at 33 degrees celcius idle with a stock 1.8ghz celeron cooler (my normal heatsink had a gap between the cpu after I pulled the IHS off).
EDIT-Oh did I mention I dont have a case? lol.
Nevermind those temps, it idles at 23-25 degrees celcius. I think the fact the ac kicked in and nothing running on the pc helps.
i3 540 @ 3066 MHZ
4GB DDR3 1600 1T 9-9-9-28
HD 5750 @ 850/2400
Antec Lanboy Air