Rather than having to fiddle with a cable and finding a USB connector or outlet nearby, you could be charging your phone with one of these very convenient induction charging devices that let's you simply drop 'n charge...
Powermat Wireless Charger
For $49 you get a special case for your phone and the charging station that works thru the magic of induction. You just place it down and the charging starts immediately, with a magnetic alignment system which insures all your charging contact points meet. Powermat's RFiD handshake technology also makes sure you don't waste power by checking how full your battery is, turning off when it's fully juiced.
WildCharger Wireless Charger
Charging your phone is as simple as placing it onto the baseplate, outfitted with zero-profile conductive strips that touch the contact-point nubs on the back of the phone case. You don’t have to align it or plug anything in, simply place the phone on the base plate and it will do its thing without the mess of wires. WildCharger claims that their charger system is approved by Apple, so it should work with your iPhone without issue. The “skin” case for the iPhone cost $35.99 with the bundle for both the case and the charging baseplate going for $79.99.
CaseMate Wireless Charging
If you want a setup that complements an all-Apple setup, this is it. The Apple industrial design influenced CaseMate package includes a Hug pad and a Hug case. The former connects to a standard AC power source and the slim case provides daily protection for your iPhone while also charging it when placed on the pad. The pad will work with any wireless charge compatible case. It is based on the Wireless Power Consortium Standard, which means that the charging pad will be compatible with future products based on the standard. The System is priced at $89.99.