Every programmer should learn a little Lisp! Even if you just get through the first two chapters I think it would be helpful, and many of the ideas carry over effortlessly to Python. (Higher order functions, closures, functions returning functions, etc.) I spend most of my free time coding in Python but learning Scheme was great for me, and the styles go really well with event-driven designs you have to implement a lot in JavaScript/ActionScript.

There's also a pretty good series of recorded lectures Berkeley gives in conjunction with the book over at http://academicearth.org/courses/the-structure-and-interpret... if you have lots of free time.