I’m shopping for a Raspberry Pi power supply. They run from dirt cheap (and built that way) to about $15. In the past I have used CUI power supplies for such things. They are reasonably priced (just $1 more than the less efficient Adafruit product), have the usual bullet items (e.g. over-current protection), have level VI efficiency (>=68% at 1.25W; >=73% at 2.50W, and I have had good luck with their products.
CUI 2A Power Supply from DigiKey
If you want one just let me know.
I’ve been using this $11 one from MicroCenter.
The key here is that a rpi will not drain more power than it consumes. if you intend to power something hungry from the rpi’s usb ports (1.1A max) you may actually need a supply with some reserves. in addition, the board has a polyfuse that should prevent damage to the board on overvoltage conditions.
the rpi wiki has in-depth info on this topic.
With that in mind then one should be able to pick up the right usb power supply. Personally Samsung chargers work great in my experience: