I have no idea what I did with my college acceptance letter, but knowing me I probably lost it within ten minutes of receipt. One thing's for certain, I didn't do anything near as cool as what this young lady from Georgia did with her acceptance letter from MIT (found via BoingBoing):
Chris sez, "My name is Chris Peterson. I run web communications for MIT Admissions and have been a loyal BB reader for years. For the last several years we have been sending our admitted students their acceptance letters in cardboard tubes. First because we sent a poster, but now it's its own thing. 2012 is the anniversary of an old MIT balloon hack, so we put a letter in all of the Early Action admit tubes telling them we wanted them to hack the tubes somehow, and set up http://hackthetubes.mitadmissions.org to collect responses. Lots of them are great, but this one, from Erin King (MIT '16) in Georgia, is the best."