Just when I thought there wasn't any new hobby that could arise and completely eat up any paltry free time I might have, they make LEGO robots Mac-friendly: "The heart of the new system is the NXT brick, an autonomous 32-bit LEGO microprocessor that can be programmed using a PC, or for the first time in the retail offering, a Mac. After building their robots, users create a program within easy-to-use yet feature-rich software, powered by LabVIEW from National Instruments."
Engadget has a great video up of the different robots on display at CES that you should definitely check out.