I was looking at various makeshift methods for making stands for my iPhone, (so I can leave it on my desk and watch movies, slideshows, etc.) when I discovered that my DLO iPhone Side Case (found in most AT&T stores) makes a perfect stand:
I just open the flap and flip it over like this:
I place my iPhone in the flap crease and voila! The belt clip on the back holds up the case and the weight of the iPhone keeps the flap down. Works like a charm!