Question: Which video adapter or cable do I need to display my iBook's screen or play a DVD onto a TV?
Answer: The VGA adapter that comes with the iBook is only for a computer monitor, you will have to purchase the correct video cables and/or adapter for your model iBook to get video out to your TV.
If you have a clamshell/colored model or a 500-600MHz iBook with 8MB VRAM iBook with a DVD or "combo" drive, then you have an A/V port instead of a headphone port. You will need to use the Apple A/V Cable, (Apple Part #: 922-4559) to get composite video and audio out of your iBook. You do not need to buy any other cables.
If you have a 600, 700, 800 or 900MHz G3 iBook with 16MB-32MB VRAM and no external reset button or a G4 iBook, you will need to use the Apple Video Adapter to get composite or s-video jacks for video out of your iBook. You will also need to buy a composite (RCA) video or s-video cable.
Because the Apple Video Adapter is video only, you will also need to buy an audio Y cable to get the audio out of your headphone port and into your TV. If you have already purchased an Apple A/V Cable and your computer requires the Apple Video Adapter for the video, you can still use the A/V Cable for the audio out of your iBook.
If your TV does not have composite or s-video inputs, you will have to buy an additional adapter. There are "RF Modulators" that will take the video cables and convert the signal for your cable input and there are other adapters for your SCART input (however, I've never purchased one, so you might have to search for that yourself!)
Apple's Knowledge Base Article HT2721 has some good information (and pictures) of the different video adapters and the resolutions they support.