I don't have representation yet and I am looking for castings online. I cannot find any that are specifically for voice over in my area or in L.A.
Are there any sites that cast for JUST voice over?

Voices.com and voice123.com are the two off the top of my head. Search "voice" on the message board homepage and you'll find included in the results my concerns about using them. However, my concerns may not be yours.

You might try your local call boards for your area. Here, I heard you need an agent to get basically most of them, unless the companies make it a open call.But you'll need a voice reel to give them.