As I mainly work on web applications, I was pleasantly surprised to hear about the Web Platform initiative by W3C. It looks like WebPlatform.org aim to become the one place web developers go to for information. Knowing how much time I spend looking for information about how to get a given feature looking and behaving the same in
all most web browsers, the aspect of having a one-stop-shop entices me!
Being in an alpha state there is certainly a lot of room for adding more / improving the information already there, but since the biggest companies within web development are on-board (Microsoft, Google, Adobe, Apple, Facebook, etc.), and it is being maintained as an open wiki (that anyone can help improve), this might just become the greatest web development resource out there.