Originally Posted by duranza
So what is the best way I can use my unusable 15,000 United miles? I am not planning to fly United in the near future and would rather use them for car rental or hotel stay. Any tips? 
If you have a Diner's Club card, you can transfer miles from United or American to Diner's Club Rewards points. From there you can transfer to just about any airline. I've only done this with American, but you will lose 50% of your miles when you convert back (2 miles = 2 DC points = 1 mile). Diner's does have promotions sometimes where you will get better than 2 points/1 mile.