Corondo Springs does sell mugs that can be used at Pepper Market and the Siesta Poolside. Also unlike the other Resorts which sell a generic mug design, their mugs are the Resort design because their dining locations are not owned and operated by WDW.
Hey! We stayed at CSR back in May and LOVED it! You can click on the link in my signature to read our trip report if you'd like. It has TONS of CSR pictures.
By the way, here is a picture of the CSR mug:
Also, there is a GREAT CSR thread for pictures. Some of them are absolutely breathtaking. Here is the link: