500,000 stocks available to short: <a href="http://www.interactivebrokers.com/en/trading/ViewShortableStocks.php?key=spng&cntry=usa&tag=United+States&ib_entity=llc&ln=" rel="nofollow" target="_blank">http://www.interactivebrokers.com/en/trading/ViewShortableStocks.php?key=spng&cntry=usa&tag=United+States&ib_entity=llc&ln=</a>