Anyone outside the USA who owns an iBook may have noticed that fullscreen applications will switch to NTSC when plugged into a PAL television. The result is your favourite game, etc, runs in black and white on the TV.
I've written a small app called PALifier that will check the video mode when the TV is connected. If any application changes to NTSC, PALifier will change the video back to PAL (at the same resolution and colour depth).
It's free and available through the above link.
[Editor's note: I don't have a PAL television to test this on...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020219004849930