Looking into this a bit more I was surprised at a few things. In another thread Hitman suggested Sharebuilder for noobs like me to check out stock so I went there.
Can't purchase Willem Hill stock through sharebuilder. (Maybe cause it's a UK company? Will that change after they complete the buy out of Leroy's?)
CET and Cantor are privately owned (I did not know this)
So of the big casinos it looks like MGM, Wynn, LVS and Boyd were only ones I could find.
I'm sure MGM will be involved in any online deal even if it's just poker. Wynn and LVS could as well.