L'Oreal True Match concealer is really good. (And it's TRUE, it matches any skin tone. HA HA.

Me and my bad attempts at a joke! LOL I think True Match is 7-9 dollars.
Another one that's super amazing is Estee Lauder Double Wear concealer. It's pricey but amazing. 19 big ones!
Good Luck!
Here is a girl reviewing True Match and talking about the foundation. She's really good.
http://www.youtube.com/watch?v=E4d9msGJnug