You probably won't be making Sundance-worthy movies with your iPhone, but if you need to keep it stable for, say, FaceTime, here's an easy way to mount it to a tripod using a cheap mount, some glue, and a nut.
If you don't already have a suitable car mount or phone case, the cheapest model will work for this—it doesn't need to be industrial-strength or anything. All you need is something to keep it stable. Then, just get a nut that fits your tripod plate and glue it to the phone holder. Now you can just screw your phone onto the tripod like you would any other camera.
Got any other tips for keeping cameraphones stable? Share them in the comments.
DIY iPhone/Smartphone Tripod Connector [Instructables]