[thephyber]

A former coworker makes liberal use of American Express disposable credit card numbers -- proxy credit card numbers that you can request to give away to less than trustworthy merchants.

[jacobwg]

Privacy (https://privacy.com/) offers a similar service for those that want something that works with more than American Express cards or other such offerings from other card issuers.

[phs318u]

Did not know about this! Checked it out, got really excited... and then discovered it's US only :-(

[geostyx]

I use this all the time. It's great.

[tatersolid]

My Citibank card has the same feature, although the number generation applet requires Flash. On a banking website. In mid-2017.