Some useful links from around the web for new and experienced brewers alike
Brewer's Friend: A useful repository of recipes, calculators and information
How to Brew: John Palmer's definitive guide to brewing at home. Step-by-step instructions for getting started with extract and all grain. Required reading for new and experienced brewers alike.
/r/Homebrewing: Reddit's homebrewing community
Malt Comparison Chart: Looking for a suitable substitute for a particular malt? This handy chart provides a cross reference of styles available from the most popular maltsers. Courtesy of the Knight of the Mashing Fork, a central Connecticut homebrewing club
Wyeast Yeast Strain Guide: An overview of the complete range of Wyeast strains
Hops Varieties: Comprehensive flavour and use profiles for most available hops
Hop Substitution Chart: Courtesy of brew365.com
brulosophy.com: Possibly the most informative homebrewing blog around. Check out the library of past ExBEERiments.
BIABBrewing.com: If you're ready to make the leap to all grain, but can't afford the space and cost of a mash tun.