The Postal Service really benefitted from its partnership with Pixar: we are not paying for use of the characters or for the creation of any of the advertising. The Toy Story 3 characters are also featured in a line of birthday cards that are sold in post office lobbies.
Here's the latest print ad:
And you also check out the newest site for Priority mail, http://www.prioritymail.com/. Once there, you'll see some really cool things: Woody's Road Trip game, a virtual box simulator, and a way to order your own free priority flat-rate boxes. Here's a screenshot:
