Frames are all well and good, but aren't always an option. Sometimes it's because of an oddly-sized print, sometimes frames just cost too damn much. How do you hang a print when you can't find a suitable frame?
Binder clips or clothespins and string
A few Homies posted their clippy solution in our Flickr group, and when paired with the right surroundings, this technique works beautifully. This looks like a textural oil painting — a fantastic juxtaposition against shiny office clips.
If the art is thin enough, it can be mounted. There are lots of options, depending on how permanent a solution is desired. Starting with a piece of plywood from a lumberyard (birch ply is nice, and about $8 for 24"x24") or a blank canvas from Plywerk (or cardboard or acrylic or masonite), you can adhere the print using spray adhesive, double-sided tape or photo corners.
Just liked Dale did in her mantle makeover, you can lean art against the wall on a shelf or mantle.
What else you got? When frames failed you, what was your solution?