To embed youtube videos, you just put the youtube code around the Video ID number (NOT the full URL). So, for example, to embed your first video at
http://www.youtube.com/watch?v=ubWl1xB9KyI , you would put in the following:
HTML Code:
[youtube]ubWl1xB9KyI[/youtube]
Doing so, will properly embed the video like this: