To narrow down the question, please suggest web-based topics only. To be honest, I'm struggling to find one for myself :)
I'm doing Computer Science and looking for a web-based, individual project. A suitable topic would have a certain degree of novelty, so while you guys browsing the web everyday, what kind of things you expect but haven't come up before. Sorry for my lousy English :)
Though there are a couple new projects out there along these lines, a great web based project could be a web based integrated development environment. I've been wanting a good one for a while, and people just haven't quite gotten them up and running yet. If you do this, concentrate on just one language (but keep it modular enough to add other languages later), the coding will be challenging enough as is. I would only suggest trying this if you want a challenge; if you complete it, it should provide a decent base in web/gui application development.