Rounded corners for video

As in matte half circles onto video clips or actually create an MOV with non-square corners? The former you could do by making a black shape in Photoshop or in Motion and superimposing it over your clip in FCPX. The latter you would probably need to do some custom programming as video clips in QuickTime are always squared off on the corners.

If you want something quick, cheap and cheerful there's an effect called "crop and Fearther" that can put a black border, variable width around the edge, and you can round the corners. Just have "feather" set to 0.