For complete start from scratch sites, it depends on what language you wanna learn. I wrote a series of tutorials and found some others and made a site, if you want to learn Java.

When I was in 10th grade my buddy and I would get homework assignments that students from a year or two back did. Then we'd put em up on a geocities page for everyone to get. It was good fun. You can learn PHP too, which might make something pretty cool. Create a site using PHP, and have a form accessible to submit homework files. So one person can do the homework, and upload it via this form and script, and everyone else can download it whenever they want. You can store the entries in a database and organize it really simply and easily. That would be pretty cool.