Audio chat from Mac to Windows??

The best way to go about voice chat between different platforms is to use an app that supports "SIP" (session initiation protocol) try X-Lite from http://www.Xten.com/ you can get same app for win and mac, you'll have to sign up for a sip number, i'd recomend "Freeworld Dialup" http://www.pulver.com/fwd/ you can then call between a pc and mac like a phone (its free too), and with the use of other third party services its possible to make a standard land-line phone divert to your computers sip number.

Bye

Wait like a week or two. Skype for Mac OS X will be out. The windows version is excellent. The Mac version will be killer!