A quick tutorial showing how to set up Apple's Compressor to downconvert from 720p60 (HD) to 480i60 (SD).
If you simply use the DVCPro50 preset that comes with Compressor, your video won't be interlaced (half of the frames are thrown out). This video tutorial shows how to enable interlacing so you can take full advantage of having 60 frames per second.
A quick tutorial showing how to set up Apple's Compressor to downconvert from 720p60 (HD) to 480i60 (SD).