Got my Ravelry invite last week (my ID is huckleberrymama) and it was fun till today. I've started listing my projects, looked at other people's projects with the same yarn to see what needle size they're using, and browsed for sweater patterns for my kiddo. A really nice resource, with cool features like automatic links to people's Flickr accounts and their blog posts about their projects, so you can really get a good sense of how a pattern will look in a variety of yarns and what sort of pitfalls you might run into while knitting it up. It organizes the enormous explosion in knitting blogs and photos in an incredibly useful way. Plus (NERD ALERT) I like looking at what my friends are working on, and what yarn they just bought.
But then today I fell in love. I discovered the ISO/destashing board. Now that's the way to a girl's heart. Not to mention her PayPal account.