- MacBook Pro with Core 2 Duo
- MacBook with Core 2 Duo
- Mac Pro
- iMac with Core 2 Duo (not the 17-inch 1.83GHz model though)
Airport Extreme 802.11n Enabler for Mac is available now for $1.99, and since it is a download you can get it within moments of paying for it.
Update: As has been pointed out (and which I took for granted), if you are planning on buying one of the new Airport Extreme base stations you need not buy this separately. It'll come with the base station.
Thanks to everyone who sent this in.