http://www.google.com/support/youtube/bin/answer.py?hl=en&answer=75301
Is it possible to add '&rel=0' to turn off related videos?
<object width="425" height="350"><param name="movie" value="http://www.youtube.com/v/xxxxxx<strong>&rel=0</strong>"></param><param name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/xxxxxx&rel=0" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"></embed></object>