During my freshman year, I was a developer at CalCentral, the new official portal for students at Berkeley. It’s pretty, it’s functional, and it’s open source.
Probably the coolest thing I did at Calcentral was embed this map of the school which tells you where your next class is:
Besides that and bug fixes, one of the features I was responsible for was the book list for a semester. The feature is live now (it’s pretty useful at the start of a semester!)