Not sure if this is the correct place to post this, if not I am sure the Mods will move. Just wanted to share the following link for a sale on the Energizer XP8000 portable battery at buy.com. I saw it on their daily deal email today, and it is half price compared to if you go to the site and search for the item.
Buy.com - Energizer 8000mAh Universal Battery Pack w/IPad tip
I have not tried this, but figured if it could power a netbook and ipad, it should be more than powerful enough to provide multiple charges to a smartphone.