After programming for several years with PHP and JavaScript for work, I've decided to "exercise" my brain a bit by picking back up some Java, JSF, Hibernate and a slew of other obscurely named APIs.

So far it's been fun reading up on everything again.  It feels like I'm learning an entire new language, but at least the courses I took at PSU gave me a foundation.

If that's not enough I've also picked up playing the piano recently to help stimulate the left side of my brain.  It's interesting how your brain can understand that you need to play two different notes on your left and right hand, but your body can not react fast enough to it without training.