How do I avoid or get past the post-orals slump? I just passed my comprehensive oral exam. I took a week off and have spent the better part of another week trying to build motivation to get back to work. 

Now I have about a dozen things I could do for my project: delve into the observational or modeling literature, hunt down a tricky bug in my prototype model (several approaches!), derive the more general governing equations for my dissertation model, learn somebody else's code which I plan on basing my model on, restructure my prototype code (needed, but it'll take hours), and the list goes on.

I acknowledge that this is a broad and opinion-based question, but here goes:

What are some good ways to beat the post-orals slump?
The most urgent thing to do is to take a short vacation and celebrate. Go do something fun, unrelated to your research. If you live near a beach and the weather is nice, sit on the beach with a non-technical book. Go to any local tourist attraction. Eat a nice dinner with friends. Watch a movie. 

A few days delay will not cost much, but could bring enormous benefits in your readiness to get on with the next steps.