[pcw]

Does such adapter exists?

I would love to have one because I'm using my MacBook connected to an external monitor and then have the MacBook connected to the TV in my living room.

If that doesn't exist perhaps a VGA to VGA and S-VIDEO adapter exists? (since I already have a Mini-DVI to VGA from Apple, I could use that and connect it to VGA and S-VIDEO).

[Thraxes]

Well aside from the apple mini-DVI -> SVideo / composite adapter, what you are asking for is a "scan converter" to convert VGA to normal Video. Best to just google it, but be prepared to spend at least 100$ for a decent one.