These sites provide an abundance of help, advice and inspiration.
Ravelry - superdooper pattern library, a million people to answer your questions and share your knit/crochet life, helpful notes on other people's projects, masses of brilliant stuff. The best website, in the world, ever.
KnittingHelp.com - videos walking you through lots of different techniques. If you can't find what you want here, there's thousands on YouTube. Ann Kingstone also has excellent videos to walk you through certain techniques, especially useful for Fair Isle (navigate using the tabs at the top).
Knitty - online magazine, the articles are excellent.
UK Hand Knitting Association - techniques, UK competitions, communities, shows, jobs and all sorts.
TechKnitting - exceptional blog explaining the ins and outs of different techniques.
The Knitting Fiend - a multitude of calculators, e.g. how to decrease stitches evenly across a row and how much yarn is needed for a project.
Left-handed knitting - lefties, you have a choice of knitting the same as righties, standard English style or standard Continental style, or "mirror knitting". If you knit the standard way you'll find masses of instructions and advice (many people prefer the Continental way as the left hand is used more). If you mirror knit you may find the movement more natural, but righties will be flummoxed to help you. Find out about mirror knitting.