Nowadays you can walk into most any Rite-Aid, Safeway, or Albertsons and plop down $10 for a prepaid mastercard. You can place funds into your account at any of the stores that sell the card. Monthly fees are about $5 and it costs about $5 each time you deposit money into the account.
I use mymccard_com for most of my online domain purchases. That way, I can keep almost a zero balance on my card until I need to make a specific purchase at a specific time. It helps to keep me from getting ripped off.