You should read this blog post by ‘Frequent Miler’.
He describes Evolve Money, a new service that will let you pay bills (for free) with prepaid debit cards and gift cards. It’s a great way to liquidate those.
They don’t publish a comprehensive list of the bills they let you pay. This service is a loss leader for them so they don’t just let you add your own merchants to pay.
But you may be able to pay your mortgage, even, with a mileage-earning debit card (like the Suntrust Delta debit card) or liquidate a MyVanilla Debit card (that you funded with Vanilla Reloads) or even MasterCard/Visa gift cards that you purchased with a credit card at a store where you earned bonus miles.
You’re allowed $1000 per day in bill payments currently.
As they say, read the whole thing.