If you received a new Kindle for Christmas, you may find that there was only a charger for use with your computer (USB cable) included. There are lots of forums that discuss using a phone charger for your Kindle. The general consensus is that you can use another charger (your phone charger should work) if it is 5v (i-Pad charger is not recommended).
I'm using the adapter/charger that came with my LG Xpression phone.
Also, if you use the USB cable with your computer, you may find that not all USB ports will act as a charger. See report here.
Amazon has detailed information on using and charging your Kindle here.
If you have any other Kindle tips, I'd love for you to leave a comment.