This will take a series of youtube videos and play them sequentially.  It is incredibly simple javascript, but I couldn't find snippets anywhere else, so here you go.

MIT license 2012.  Do whatever you want with this.

use this by calling init() with a series of YT ids, as follows:

init(["cEwmywm6S7k","Ma7lyfYzIw8"])


DEPENDENCIES:

http://ajax.googleapis.com/ajax/libs/swfobject/2.2/swfobject.js