DIY Net-radio sites aren’t exactly exotic these days, but few are as easy to use as myCaster, which allows you to build radio playlists by simply dragging MP3 files onto the custom software (a lickety-split 320K download) and…that’s it; myCaster enters your show into its searchable database, and you’re free to focus on your voice-over: Just click on a button to overlay the tunes with witty commentary. Or make like a real DJ and spout inanities.