Listmania!
Survey of programming languages/paradigms
By an Amazon.com customer
Haskell: The Craft of Functional Programming (2nd Edition)Haskell: The Craft of Functional Programming (2nd Edition) by Simon Thompson
Buy new: $48.36 / Used from: $40.99
Solid introduction to Haskell and functional programming in general, though a bit cluttered with SICP-esque exercises for my taste
Programming Ruby: The Pragmatic Programmers' Guide, Second EditionProgramming Ruby: The Pragmatic Programmers' Guide, Second Edition by Dave Thomas
Buy new: $29.67 / Used from: $8.49
Excellent introduction to that up-and-coming language Ruby and gives a couple good examples of metaprogramming
Programming in Lua, Second EditionProgramming in Lua, Second Edition by Roberto Ierusalimschy
Buy new: $26.37 / Used from: $19.97
Much better than the reference manual for getting the flavor of the language and how to actually program in it. Really gives you a good sens of Lua's minimalistic, unique style.
Classic Shell ScriptingClassic Shell Scripting by Arnold Robbins
Buy new: $18.84 / Used from: $13.00
A good tutorial on sh syntax and using standard unix commands (cut,grep,sed,etc) both interactively and in scripts. Also good in a reference capacity for the various arcane commands.
Python in a Nutshell, Second Edition (In a Nutshell (O'Reilly))Python in a Nutshell, Second Edition (In a Nutshell (O'Reilly)) by Alex Martelli
Buy new: $26.39 / Used from: $16.00
The official Python tutorial is really better for learning Python, but this book is a very good reference that explores some of the more advanced subjects in Python. Python is surely one of the most elegant languages ever designed
Practical Common LispPractical Common Lisp by Peter Seibel
Buy new: $58.49 / Used from: $37.96
An pretty good primer on Common Lisp and some of its libraries, though a bit heavy on examples as would be expected by the word "practical" being in the title. You'll seen that Greenspun's 10th Rule really isn't so much a statement on wheel reinvention as it is a testament to everything they managed to cram into CL.