You can eat at any counter service listed on the plan (which is pretty much all of them). Everyone on the plan gets a drink, entree, and dessert. Like at Tusker House (my favorite) I got drink, rotisserie chicken w/ vegetables, and carrot cake. For CS, I recommend Cantina in Mexico, the chinese CS was good also, there are several in the world showcase I want to try (everyone raves about Morrocco). In MGM, stay clear of ABC commisary - I have heard good things about Flatbread studio. In MK, we liked Pecos Bills, Columbia Harbor House, and I have heard that Cosmic Rays is good. In AK, Tusker House and Flame Tree Barbeque.
As far as snacks, it is pretty much anything under $4. Many people use the snack credits to pick up disney candy to bring back for souveniers. Below is a link that list snacks. Let me know if you cannot pull it up. I am not sure if I did the link right!

I am a tech idiot! I got the list from here somewhere. It lists all the snacks you can get on the DDP all over WDW!
Hey, I just checked and the link works! I have learned so much on the DIS!
http://personalpages.tds.net/~rb/DIS/MYW Dining/WDW_Snacks_2006.htm