It's Mac OS X 10.4, the latest version of the OS. All versions of OS X have their own cat name, but it really wasn't used in promotions until Jaguar.
10.0 = Cheetah
10.1 = Puma
10.2 = Jaguar
10.3 = Panther
10.4 = Tiger, coming 2005, me thinks
Look how far we've come since I last installed Windows
BTW, added the attachment I forgot. WIDGETS!