I've got (or have used) one (or more) of each modern series 7200RPM/ 8MB cache drives). I must say the WD800JB has a pretty mechanical (and annoying) idle spin to it. The seek noise is also pretty loud. The Maxtor DM9+ (Mine is 160GB; dual platter) seems to be a tad quieter than the 800JB, but it still requires AAM to subdue the pretty annoying (and audible) seeks.
Now, the 7200.7 80GB I have is very quiet. The idle noise is very low, and I have never heard it seek until I put it in my SFF (with a 15dBa PSU fan and a heavily undervolted Panaflo L1A). The Samsung 160GB / 8MB drive is also really quiet (quieter than the Maxtor and WD) with virtually inaudible seeks.
Cliffsnotes: Samsung and Seagate are quietest. Others are saying WD and Maxtor drives are quiet, but you can clearly hear the seeks in a relatively quiet PC.