Over the past couple of months, I've been using what little free time I have to code a website called Clustur. It is located at http://clustur.com. The main page pretty much says it all, but it's basically a site for creating, learning, and sharing study material. I've recently used it to study for all of my exams this semester. Because it passed the test of exams for me, I can say it's helped me a ton during the process.
It's coded in Django, which helped a lot because I was able to use much of the built-in functionality. Right now it's still hosted on my home server, which is slow as molasses. Once Clustur starts getting used by people, I'll move it over to a WebFaction server. I'll also admit that it needs a bit of user interface tweaking, but for the most part everything is solid. I also have some great plans with which to extend this site, but I'll let it be a surprise when they are ready to release.
It's coded in Django, which helped a lot because I was able to use much of the built-in functionality. Right now it's still hosted on my home server, which is slow as molasses. Once Clustur starts getting used by people, I'll move it over to a WebFaction server. I'll also admit that it needs a bit of user interface tweaking, but for the most part everything is solid. I also have some great plans with which to extend this site, but I'll let it be a surprise when they are ready to release.