Hi, there are a lot of people adding links to YouTube, but few are inserting the movie inside the forum.
Here are how to.

Example code, insert it right into the message:

[FLASH_VIDEO]<object classid="clsid:d27cdb6e-ae6d-11cf-96b8-444553540000"
 codebase="http://fpdownload.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=8,0,0,0"
 height="385"
 width="640"
><param name="allowScriptAccess"
 value="never"
></param><param name="wmode"
 value="transparent"
></param><param value="never"
 /><param value="transparent"
 /><param value="never"
 /><param value="transparent"
 /><param value="http://www.youtube.com/v/v-_lbrBeNOw?fs=1&hl=en_US&rel=0"
 name="movie"
 /><param value="true"
 /><param value="always"
 /><embed allowScriptAccess="never"
 type="application/x-shockwave-flash"
 wmode="transparent"
 pluginspage="http://www.macromedia.com/go/getflashplayer"
 height="385"
 width="640"
 src="http://www.youtube.com/v/v-_lbrBeNOw?fs=1&hl=en_US&rel=0"
 /></object>[/FLASH_VIDEO]

To add your video, just edit this code twice in the script above:

http://www.youtube.com/v/v-_lbrBeNOw

Result is like this: