There are 2 Types of Prepaid Card.
1.) You can buy them at almost any Retailer. Example: WalGreens, WalMart, Staples etc. There is an Activation Fee upon Purchase. Once the Activation Fee is Paid the Card is Active. These are Non - Reloadable. Once the Funds are Depleted the Card is Finished. (These may Work with RLC and they may not)
2.) You can get a Prepaid Card directly from your Banking Institution or any Pay Day Check Cashing Outlet . These Cards will be Re-Loadable where you can add funds to it as you wish to a certain amount set by your Bank. There could be a Fee involved but it depends on where you get it from. (These Type of Cards should work with RLC)
I use a Pre-Paid Card for all my Online Purchases but have never used them to Register on any Websites.