PostScript

• PostScript Language Tutorial and Cookbook - An introductory text, known as "The Blue Book" on account of its covers. Highly recommended.
• PostScript quick reference sheet
• A First Guide to PostScript (University of Indiana)
• All about Ghostscript/Ghostview (University of Wisconsin)
• Links to PostScript references
• Another first guide to PostScript
• A PostScript IDE is available.
• PostScript Language Reference, third edition - (PDF) of the language definition, known as "The Red Book".
• PostScript language program design - "The Green Book".
• Adobe: PostScript vs. PDF - Official introductory comparison of PS, EPS vs. PDF.
• A First Guide to PostScript - Another first guide to PostScript.
• Mathematical Illustrations: A Manual of Geometry and PostScript - Nice pictures!
• Thinking in PostScript - by Glenn Reid, Addison-Wesley, available online courtesy of the author. A thorough tutorial.

Scheme

• Revised^5 Report on the Algorithmic Language Scheme
• Scheme page at Wikipedia

Haskell

• haskell.org
• Yet another Haskell Tutorial
• Learn You a Haskell for Great Good!
• List of Haskell tutorials
• The Evolution of a Haskell Programmer

Prolog

• SWI-Prolog
• A Prolog tutorial from Cal. State Pomona
• Learn Prolog Now!
• Another Prolog tutorial from Laboratoire d'Informatique de l'Ecole Polytechnique

Python

• http://www.python.org/doc/ -- the Module Index linked to from this page is very handy
• http://docs.python.org/tut/tut.html -- a Python tutorial
• Python Executive Summary -- http://www.python.org/doc/essays/blurb/
• Python Quick Reference -- http://rgruet.free.fr/
• http://www.python.org/peps/pep-0008.html -- a style guide: covers indentation, use of tabs and spaces, etc.
• Book chapter with examples of file I/0

Java

• The Java Language Tutorial (from Sun - it's comprehensive)
• Cafe au Lait