Khan Academy is also in-browser project based. I think it supplements learning, but they don't really push the boundary. Like for Code Academy (which I forgot to mention before), the exercises were very simple and I didn't think they pushed me to think harder. Way too easy. I want very hard projects/exercises but I also want them to give me study materials that will help to me understand the problem. Code Academy won't make anyone a serious programmer, probably not even a hobbyist.

The other two mentioned, I never used them before. I might check them out.