[unimpressive]

I would probably learn nothing because I'm an easily distracted Internet addict. But if I could force myself to do something:

I'd learn more about distributed networks and *nix shell. Mainly because I have project ideas that require knowing both very well.

This is a really context-specific question. I don't think theres any general thing that everyones out to learn. Learning is (at least for me) a really goals oriented endeavor.