Do a search... lots of posts about this very subject. Hella and Piaa are probably going to get the most votes, though Piaa are generally quite a bit more expensive than Hella. KC, IPF, and Catz might also get honorable mentions are are also good.

It all depends on how big a light you want, round or rectangular, and how much you want to spend.

Hella 500s and 550s are pretty popular, and can be purchased for ~$70.