I've had no big start-up yet, but I've found mini-start-ups a great motivation and learning experience. If you have something that you want to make you can learn while you make it, it will give you the motivation you need to learn (get your site done) and it will provide a great learning environment (building your product).

I'm in school for web development, since I got the basics of programming down in my second semester, I've learnt more from my own projects then school.