C language:

C Library Reference Guide

C language tutorial

Programming in C Notes

Animated basic C tutorial

Debuggers:

gdb tutorial

gdb for the unix newbie

dbx tutorial

Java:

Java Language Specification

Unix:

Unix Tutorial for Beginners (U. Alberta)

       Cal Tech Big Unix Tutorial

A Unix Course at Ohio State University

U Texas Unix help

Emacs:

Emacs User's Guide (U. Southern Maine)

lex/flex tutorials:

        creating a lex scanner

Lex - a text scanner (lots of useful information here, with examples for makefiles)
   flex (a scanner generator) tutorial
lex and yacc FAQ

JLex: A Lexical Analyzer for Java

Webpage Design

Tips for writing webpage content backed by research

Research-based Web Design & Usability Guidelines