Directions:
Goto www.youtube.com, find a video and click on view source. Search for SWFObject or player2.swf in the file. Grab all the text starting with video_id and after. This is the file you want, attach that to http://www.youtube.com/get_video? and drop it into this box to generate the link for you.
UPDATE: Format change. You should see a line that looks like this:
var swfArgs = {hl:'en',video_id:'gDfKCzMuLMc',l:'223',t:'OEgsToPDskLWJws5s_H1Qlsjo-I3I900',sk:'Qm6O8wb8RD6YCAISJuzG7AC'};
Start again with the http://www.youtube.com/get_video? and add in the video_id, l, t, and sk by putting in &l=, &t=, and &sk= in added in after the video_id was put on the end.
Example: http://www.youtube.com/get_video?video_id=AYxu_MQSTTY&l=283&t=OEgsToPDskImLbnqsgx8Uxct1XFa_eVw&soff=1&sk=N8E5Z-YSJ8r9mc0PzVcVlAC