ZNGA currently has two web sites dealing with gambling, ZyngaPlusPoker and ZyngaPlus Casino. These sites should launch sometime in June. Also, their other platforms for PC downloads and Facebook will launch, hopefully, no later than July/August.
As for online gambling in the US, this is about a year to 3 years out. Feds have to get behind it. Zynga is currently applying for a gambling license in Nevada, which will take months to do. Yes, individual states can approve online gambling but it's not worth offering gaming to such a small audience.
I should add, Glu is in the UK with online gambling partnered with Probability (announced in Oct 2012). And Glu as bought in to Bee Cave. The founders have developed online gambling games and use to work for Zynga. I think both companies are worth buying and holding, particularly at these prices. Hey, it's worth a gamble.