Ravelry - a knit and crochet community
At long last, a social network that I can actually USE! Ravelry replaces my tattered and ill-kept knitting project journal with an online version that plays nice with Flickr -- allowing me to compulsively catalog each stage of each project, keep a queue of what projects I've got coming up, catalog my stash for trades/sales/destashing and log my pattern books. I can also search for who else has knit any pattern and see what they have to say about it, any modifications they made, etc. It's more useful (in a hundred ways) and actually takes less time than maintaining a manual record. Yay, technology!