What could I do in Miami in 3 days that wouldn't involve partying?
 

Something interesting, museum-ish, intellectual-ish?

There's an art deco walking tour on South Beach. www.mdpl.org
The Wolfsonian on South Beach is interesting. wolfsonian.fiu.edu
Vizcaya is lovely. www.vizcayamuseum.org
The gardens at Fairchild are world class. www.fairchildgarden.org If the Chihully glass is still here when you visit, then that's a special treat.
Don't forget the Everglades (okay, that's nature but it is the only habitat like it on earth.)

The historical museum of south florida does wonderful tours with a local historian, Dr. Paul George.
http://www.hmsf.org/programs-tour.htm

The Deering Estate is a great example of early Florida architecture in a beautiful, natural setting. It's our favorite place to go for picnics.
http://www.deeringestate.com/park/home.html
Great bookstore - Books and Books. There is one in Coral Gables, one in South Beach on Lincoln Road, and one in Bal Harbor. Visiting authors, poetry readings, etc.
http://www.booksandbooks.com/NASApp/store/IndexJsp
Here are some other of our local museums:
http://www.miamiartmuseum.org/
http://www.bassmuseum.org/
http://www6.miami.edu/lowe/

Have fun!

If you have your own transportation do a day trip to the Everglades National Park. That will stimulate your intellectual-ish.......

http://www.nps.gov/ever/

I'll second the recommendation for the Fairchild.

In addition to recs for the Wolfsonian, Vizcaya, and the Deering Estate, there are many special events during the year such as the Miami Book Fair that may interest you. Check the convention and visitors events calendar for info: http://www.gmcvb.com/visitors/