my roommate's father designed a loft out of metal piping to hold up two twin beds. It was pretty sweet because it gave us a lot of room to put a fouton one year, dresser and a hammock the next etc underneath. Both beds have their own ladder ( we just used one to conserve space) and their own wooden shelf for alarm clocks etc.
Takes a bit of college aptitude to put together, but is very very sturdy ( as college students need) and not fustratingly hard.
email me for pictures/ to talk about it, since it is super high quality we have to ask a bit more for it (lofts are kinda one of those things you want to trust