I live in an apartment and I have been mulling on several different ways to hang art on my temporary walls. I use a lot of push pins to hang things because they are so simple and easy to use. Because of my method of hanging my framed art is usually very light and I use large, hippie tapestries to spice up blank walls (Don't judge. They make nice table cloths and decorative bed covers, as well).
Heather on Dollar Store Crafts suggested that you hang a wooden pants hanger to display art that changed frequently; like children's art and inspirational images.
Sean Ragan on Make suggested using a pull tab on the back of frames if you don't have proper hanging hardwear.
I like using a length of twine hung between two push pins and some clothes pins to hang paper work, like prints and doodles. This is especially good when you have all those tiny drawings after a game of Pictionary.