A few years ago there were very few places you could buy K-Cup coffee for Keurig coffee makers.
First, you may be able to pick them up with your regular shopping when you go to the grocery. Many stores now stock K-Cups. If not, you still have plenty of choice online.
Your first stop is to check out the selection at Green Mountain Coffee. This is the company that actually owns Keurig and they are the primary producer of Keurig K-Cups. You'll find they have a huge range and offer most of the coffees they roast in the K-Cup format.
If you don’t find the coffee you want there, try Amazon.com. Amazon has K-Cups from a wide range of roasters, so can choose between different coffee companies.
An alternative to shopping for K-Cups is to get yourself a My K-Cup. This replaces both the K-Cup and K-Cup holder in your Keurig coffee maker and allows you to buy or grind any coffee you like and then spoon it into your My K-Cup. (This not only gives you a wider range of coffees to try, but also cuts back on the cost of each cup of coffee.)
One way or another, you can use your Keurig to make a brew of just about any coffee you can find.
Reviews of the Keurig one cup coffee brewers:
The Keurig B60
Assorted Regular
K-Cups
Assorted Decaf K-Cups
Assorted Flavored
K-Cups