Poker1.com is the home of Mike Caro's University of Poker and other online resources. It presents the "University" with 43 (!) lectures, test and strategy articles. There are also a lot of material on odds, rules, audio/video clips, tips and other. Also offers shop and forum. Very high quality and broad scope in the online strategy tutorials. Highly recommended!
Pot Odds Calculator
Pokerabcs.com offer a beginners guide to texas holdem poker. A collection of handy articles for the newbie player and a top list of poker rooms with reviews. The site also contains a Pot Odds Calculator for Texas Hold 'Em. Enter your hole cards, then the flop and get odds of improving your hand. Enter the turn card for revised odds. Also works out minimum pot size needed for you to have pot odds when calling. Recommended.
Coach Rounder is a revolutionizing poker software tool that serves as your own private poker coach. Upload your hand history and Coach Rounder returns detailed feedback on your strengths and weaknesses along with recommendations on what you can do to take your game to a new level. And best of all - Coach Rounder is available for free.
Homepoker.com is an informational guide on poker, with directories over game variations, strategies, books, basics and more. There is some good original content to be found here.