The Betacup challenge to design a better coffee cup is underway. Apparently they have 152 ideas. You can see three of the best at Core 77.
The design above is my favorite. It doesn't require a big change in consumer behavior, it's just a more economical use of materials:
Smart. I happen to have switched to tea myself and use a travel mug.
The cup is 100% recyclable, made as one component, in one mold with one material, black polypropylene. The lid hinges, and plastic ribs around the cup's circumference create a cool outer surface.