[chill1]

I don't have any websites bookmarked that employ such scripts, but DuckingIt (tm) yields the following links on that topic:

https://bitcointalk.org/index.php?topic=9042.0

http://www.bitcoinplus.com/miner/embeddable

https://github.com/progranism/Bitcoin-JavaScript-Miner

You should probably not embed such scripts into your website(s). If it's not illegal, it's certainly super shady, and an extremely inefficient method of mining bitcoins.