I too recommend the NextVision series of products. Find them on eBay. I got lucky and got an N6 for $125.00 off eBay.
Be warned you will have a miniscule amount of lag. According to Guitar Hero 2's latency checker, it's about 30 ms. Now, this is with composite cables on a PS2. (I also hook up my GameCube with it)
Component cables SHOULD be able to go down to lag free because the signal stays progressive from the Wii to whatever adapter you choose to the monitor. That is what I have been told at least.
Anyways, I find 30 ms of lag completely playable, playable as in it's just like playing it on a TV.