CRT TV as second monitor I want to play some 8-bit style games - via an emulator or as web games in a browser. I find that these look much better on a CRT TV. I thought of using a TV as a second monitor for my iMac (24" early 2008). It seems I need an "Apple Mini-DVI to RCA adapter" to do this.

I've tried using second monitors before but not such a lo-res TV screen. Will I be able to set a resolution and send apps/windows to this screen successfully? What is the performance/response time like? I know that plugging composite devices like Wii into digital displays can be laggy due to conversion.
That adapter will work fine. I have used the regular DVI → Composite/S-Video adapter (M9267G) many times on many different Macs.

Contrary to what has been mentioned in the comments, it is not an active adapter; it requires no external power, and PAL/NTSC resolution can be output from the iMac's graphics card. It behaves exactly as any other second screen would behave, just at rather low resolution. Performance/response time will not be an issue; there is no lag. 

Regarding resolution you'll get the option to run at native 720×576 / 640×480 (depending on whether it's a PAL or NTSC TV) or a bunch of other higher resolutions, up to 1024×768 (as far as I recall). Note that these higher resolutions will be scaled to the TV's native resolution, so don't expect to be able to read 10pt text in the 1024×768 setting.

You'll also get a fun option called "overscan" which switches between scaling the image on the display so you can see a black edge around it (like a CRT computer monitor) or so the image "overscans" and runs off the edge of the display (like a CRT TV picture).

There is a thread on mac-forums.com: the first screenshot shows the resolution options you'll see.