A Qi-compatible charger. Any of the ones listed here will do just fine, but there are many more you can choose from out there (such as this one, which retails for $12.99).
A non-metallic flexible case or cover no thicker than 5mm (only required if the receiver coil you've chosen doesn't come with a case). Remember, the thicker the case, the slower the charging.
How to add wireless charging to your iPhone
Fitting the charging coil is easy. Just pop the wireless charging card into your iPhone's connector, fold it over the back, and pop it into a case and you're done.
You do lose the port on your phone (unless you're willing to disconnect the card) but if all you use it for is charging, then this won't matter much.
With a compatible in-car charger (such as this one) you can continue to charge your iPhone when on the move.
In my experience, these wireless charging systems work very well, and are far more convenient than having to plug a cable into the handset every time. The only time it isn't is when you want to use your iPhone while it's charging, then a cable is easier.