First the PSP got handheld to TV adapters and now a nearly a year later the DS is getting them too. There are currently two different DS to TV adapters in the works. The first requires players to open up their DS and hardwire the adaptor into the console. Once installation is complete the DS can be plugged into a TV via RCA cables and both screens will be on the TV. The second adaptor is basically a camera with mirrors that straps to the top DS screen. It requires no installation, but it only enlarges the top screen. If you really want to play your DS games on the big screen forget the external adapter. It’s nearly useless since it only displays one screen and it makes the DS heavier. The internal adapter looks like it has decent quality from the single picture below, but do gamers really want to open up their DSes just to play Metroid Prime Hunters on a larger display?
Update: The adaptor is made in Taiwan by Q-Mark who has previously made a GBA to TV and PSP to TV adaptor. Here's a link where the adaptor can be purchased.
2008 update: Plenty of people found this article, which is around two years old now. The link above used to go to a product order page, but it doesn't anymore. The company who announced this plug in adapter is not selling them anymore, but the screen covering adapter is still around at some places like this site.