I use the Logitech Cordless Mouseman Optical, it works and looks great. I tried the MS Wireless Intellimouse Explorer but found it had a couple of weird quirks. For example, if you take your hand off the mouse, it powers it off to save on battery life. Not a bad idea, but when you put your hand back on the mouse, there is a slight delay in powering up. Other users have reported hearing a high-pitched whining noise coming from the mouse/receiver, but that usually goes away within a few days.
They both work under OS9/OS X, but the extra buttons don't yet work in X. The top two buttons and scroll wheel work like a charm though. Hope this helps!