I like a few of the Lisp books, which aren't very Unixy but are interesting and enjoyable: Touretzky's Gentle Introduction to Symbolic Computation and SICP, and of course the Little Schemer is a lot of fun. It's quite old but the Unix Programming Environment was one I found fascinating, and it got me into Roff which I'm thankful for. All the papers on the cat-v website are good too (I like the face server one)

I'd be interested to be read more about compilers. What are your recommended introductory texts, or is the dragon book the way to go?