I think the two really killer features are probably the most obvious one: searching and rating. If I know that the thing I'm looking for ... whether it's learni

I think the two really killer features are probably the most obvious one: searching and rating. If I know that the thing I'm looking for ... whether it's learning ruby or implementing something in jQuery, or plugging a hole in my car's tire ... is easy to find, and that what I find is going to be quality, then that site is going to come to mind quickly when I'm looking for instructions on how to do something. Stack Overflow's done this well, in that their content is so good, and so easily discoverable, that it's a no-brainer as my first go-to place for figuring out coding problems.