Is there a way to stream what is on my Mac's screen to my TV? I want to buy a Mac App Store game, but I don't want to play it in an office chair: I want to sit in front of my TV! Is there a way to stream the video output of Mac, wirelessly, to my television? The TV is currently connected to a Playstation 3, Wii, and AppleTV, and if this is at all possible, I'd like to do it without having to "hack" any one of those devices. Is there anything I can do here?
None of the devices currently connected to your television can help you display audio and sound from your Mac without hacking. And even then, it's not likely you'll get them to work as a wireless display/sound bridge.

You could use something like the Atlona PC to HDTV Wireless Adapter to send your audio and video from your Mac to your TV (that one is Mac-compatible). Are you going to enjoy this experience? I'll admit I'm very skeptical that this wireless streaming approach is going to produce a 1080p frame rate that makes you happy and comfortable playing a game. And at $200 that seems like an expensive experiment to me.

Your best bet is to get a HDMI adaptor for your specific Mac (see the Apple Store for compatible adaptors) and run the HDMI cable to your television. You can run HDMI about 50' before you need to start worrying about a repeater to ensure signal fidelity.