Solaris vs. Linux
Solaris IS free for "educational" purposes. It can do a lot more than Linux in the Enterprise environment, but the one thing holding it back is the source. Sun is opening doors to developers lately though, and maybe it'll be 100% open source someday, but I doubt it. On a Sun you can't go wrong with Solaris, but leave it at that, Linux is much better, and easier for personal use on an x86 based machine. Don't get me wrong, I like Linux a lot.