Here's what I thought of building during my college times, but never completed :P

1. A hub where students can find previous years question papers, sample papers and notes. Divide content by years, departments, etc. User management, people can share notes (a big plus point, where you don't have to upload papers). Track exams datesheet. Make a blog section to share your thoughts, and yes,. a mini quora type community. It can be extended to beyond imagination.

2. Gaming website, where you can host gaming events for college students, track their progress, updates about gaming news etc.

3. A simple reminder app using firebase and Node to alert users about, watering plants, drinking water, turning off lights, etc.

4. The coolest one, you can make InShorts clone app. I hope you know it. It's perfect and teaches you push notifications, user management and lot of other stuff.

as Bridget Sarah said , i think that's a good idea for your college.

Build Fuel manager, which will take input at every refill and show history as well as some cool summary like how many km driven, how much cost per km, how much spent on fuel..etc

and Make it as open source :D

Build a platform like Moodle, think that would be a good idea :)