New things I learned from this site were the Russian join, cable cast on and how to make a one row buttonhole (and all these techniques are awesome!) I originally came here, though, after doing an internet search on how to wrap a short row because I had totally forgotten. And then I discovered the forums and how friendly and non-snarky everyone here is. So I've stuck around since.
I also meant to say that although I was familiar with a lot of the increase and decrease methods, the idea of having one big knitted piece demonstrating all of them along with the videos is a brilliant idea. It really allows you to compare them.