www.solotrucos.org
Aca les dejo el codigo para que descargen sus videos en MP4 :

javascript:if%20(document.getElementById('download-youtube-video')==null%20&&%20!!(document.location.href.match(/http:\/\/[a-zA-Z\.]*youtube\.com\/watch/)))%20{var%20yt_mp4_path='http://www.youtube.com/get_video?fmt=18&video_id='+swfArgs['video_id']+'&t='+swfArgs['t'];%20var%20div_embed=document.getElementById('watch-embed-div');div_embed.innerHTML=div_embed.innerHTML+'<br%20/>%20<span%20id=\'download-youtube-video\'><a%20href=\''+yt_mp4_path+'\'>Descargar%20en%20MP4</a>%20'+%20%20((navigator.userAgent.indexOf('Safari')!=-1)?'(control-click%20and%20select%20<i>Download%20linked%20file%20as</i>)':('(bot%C3%B3n%20derecho%20y%20selecciona%20<i>Guardar%20'+%20(navigator.appName=='Microsoft%20Internet%20Explorer'?'destino':'enlace')%20+'%20como)</i>'))+'</span>';}void(0);