TECHknitting

With some of the clearest, easiest to comprehend diagrams out there, the author of TECHknitting aims to take the twenty-five years of knitting experience out of her mind and put it into yours, one entry at a time.
I can't imagine all the time and effort that must go into each post. Every one is a gem, from technical how tos like the continental knit stitch to frustration-avoidance posts like how to make a sweater fit to theoretical question-and-answers such as why some stitches curl and others don't. The archives are also organized nicely - you can look things up alphabetically, chronologically, or by subject. I recommend the latter to start, as even though she's only been blogging for six months, TECHknitter has built up a substantial archive of resources. Brilliant knitting site.