If you're like me, a grad student renting an apartment, chances are that you have some rather bare (and boring) walls, because your landlord (or landlady) warned you not to hammer any nails, or they will take a big chuck out from your security deposit.
How do you hang a clock then? What about some frame photos?
I found some fantastic "command hooks" by 3M which can be removed from the wall cleanly. No glue left behind. They also won't pulled wallpaper (unless it is peeling anyways). 3M also sells strips for hanging pictures, among other "command" products.