Founded: June, 2012
Location: United States (San Francisco/New York)
Coinbase is one of the larger and most established exchanges where it is possible to purchase coins via common credit cards or bank transfers. For most people (especially in the United States) all roads usually lead to Coinbase when it comes to swiping your credit card and getting Bitcoin/Ethereum/Litecoin.
Their process is perhaps the simplest and easiest to navigate. You simply sign up, enter your basic information and add a payment method. Type in how much you want to spend and coins are purchased and immediately credited to a coin wallet already set up for you.
Some of the largest merchants, including Overstock.com, Expedia, Dell, Intuit, etc., rely on Coinbase to process bitcoin transactions.
They currently only offer Bitcoin, Ethereum and Litecoin, but naturally allow easy, instant transfers to other exchanges where other crypto currencies may be purchased, with network fees applying (not those of Coinbase).
Coinbase is based in San Francisco and backed by the largest of venture capital firms in the United States.