Not a money-making site, but I figured this would be up your alley.

MaskMe let's you create 'masked e-mails'. Any time you sign-up for something, if you have MaskMe installed, instead of giving your e-mail address you can choose to 'mask your e-mail' and MaskMe will create an e-mail address that forwards to yours. If the company won't let you unsubscribe, or sells it to spam lists, you can open the MaskMe program and turn off the forwarding.

For five dollars a month, you can get MaskMe premium, which gives you access to masked phones and credit cards. The masked phones bit is nothing special, it just gives you a blocking feature. But the masked credit cards are pretty awesome. You create a credit card for any amount. MaskMe charges the card you have on file with them, and gives you a card number that has that amount of money on it. It's designed so that you can use a credit card online (or offline) without giving out any information that links to your actual accounts (or your real address or name). It's also a great way to create gift cards for people. If there's money left on the card, or you decide not to use it, you can de-activate it, and MaskMe will refund you whatever is left on the card.

I noticed some discussion recently about getting credit for trials that require a credit card and the risk involved. Those trials require a credit card, and you can easily create one with just a dollar or two on it, and then de-activate the card. So if the trial ignores you when you try and cancel, it doesn't matter, because they can't charge you.

MaskMe has an add-on for firefox and chrome, and phone apps for iOS and Android.

Ref link (gets me premium for free). Non-ref link.