Please don't respond with "just google it" or finance.google.com or some other financial website. I've already done that, but just like there are "most traded" or "biggest gainers/losers" I would like to see most volatile (over some time period).I want to start doing some options trading (specifically using a "straddle" strategy) and this data would come in handy.Only responses with "sources" please, thanks.

Try smartmoney.com or yahoofinance.com they both work very well but i would have to say google finance is very good if you know how to use it correctly.

Use a stock screener tool like StockFetcher:http://www.stockfetcher.com/