Having worked over the last couple of years in a Unix environment, just beginner stuff, moving files around, working with security/permissions, and some simple shell scripts, I now fancy learning a bit more and gaining some more in depth knowledge.

For a start I have a spare HP Microserver, and would like to install a Unix based OS on it to start tinkering, but I have no idea what to download to install on it. Can anyone advise what a popular flavor of Unix might be the most popular and best to install, preferably one that is "available" in the usual places.

I have ordered a book called "Unix power tools" which seems very highly regarded according to the Amazon reviews.....probably way over my head, but I'd like to think I am still capable of expanding my knowledge a bit.

Anyone advise what should I be installing ?