A few banks provide a system like this. I'm aware of at least Bank of America and Citi.

Bank of America calls it "ShopSafe"; you can generate a number for one-time or recurring payment with an associated limit and expiration date.

Citi calls it Virtual Account Numbers. Theirs don't have a limit by default (but you can create one that does).

Unfortunately, both systems use archaic Flash applets to generate and manage the numbers... I hate the Citi one in particular because it has sound effects when you press buttons.