try installing something like LFS (Linux from scratch) and see how much you learn about Linux. Maybe I'm just old school but even on Windows I was always studying the OS internals, the specs of the various protocols and the details of the filesystem. The difference is in Linux I have access to the sourcecode so in addition to reading a book on the specs I can study the implementation ad well.

Does this really make me a better programmer? I hope so. But it might be just an extreme form of procrastination.