For a Zalman cpu cooler the AM2 board sees a metal bracket reaching across the copper base where you either push down on that to see it snap inplace over a small plastic tab or secure it down with two screws like seen on Socket 939 models.
The large copper fins disipate heat fast! I found that out fast when one of the 110mm fan blades was found pressed in against the fins when first firing up the new build here. That saw the entire hsf heat right up. By the time the system was shutdown(like lightning there) and the side cover was offf the Zalman was room temperature. That was seen when SpeedFan and the Asus temp probe were first installed on the new Asus AM2 build here.
SpeedFan and another freeware called the System Information for Windows(SIW) have worked well and accurately for reading temps from the board's senosrs here. The Asus temp probe Probe II is also noted for accurate readings when compared to what is seen in the bios when looking at the hardware monitor there.
For SpeedFan you can find that at
http://www.almico.com/sfdownload.php The actual download link is the name seen in the second paragraph there.
For SIW which gives a complete breakdown on hardwares and softwares as well as displaying various temps for drives as well as the cpu you can find that at
http://www.gtopala.com/siw-download.html The screenshot below shows how that looks when opened and you simply scroll down to the hardware section and click on sensors to see board, cpu, and drive temps.
http://img205.imageshack.us/my.php?image=boardinfolv1.jpg