There are definitely already projects out there that will (more than likely) do everything you're currently considering. That said, there's immense benefit in doing a project like this for personal development - you get to learn, and you expand your public portfolio. If you run the project as open source, you can also demonstrate your ability to work with others. All very good (hireable) attributes.
Are there any programming languages you already know? Are there any that your course is going to be teaching that you know ahead of time?
There are so many different languages and frameworks available to choose from, but I'll only mention a few.
- Language: Framework
- .NET: ASP.NET MVC
- python: django
- ruby: ruby-on-rails
I'm a huge fan of django. Python is quite a nice language to learn. I'd recommend django purely from a biased point of view. Python runs on Windows, Linux, and Mac, though you probably don't want to host python on windows (culture more than ability).
Conversely, if you really like Windows, ASP.NET MVC makes building out websites very very easy. Mono does allow you to run .NET on linux and mac, but you might find support lacking, and I wouldn't suggest using Mono for your first project.
PHP is (was?) another popular language for building websites in. There are tonnes of web frameworks available for PHP. Popular opinion seems to be that PHP makes it easier for developers to write bad code, though it is possible to write good code with PHP.
Unfortunately, without knowing a rough direction in which you're headed, it's nearly impossible to offer some concrete advice. Database choice will generally come down to what language and platform (linux/.net) you're targeting. Web server also fits this profile. Once you decide on a language, narrowing down the other choices become a lot easier.