MilesBuzz! - Frequent Miles used on different airlines

I have miles from Northwest, United, AA and also Continental. Would like to buy 4 tickets for my whole family. I don't have enough miles from each program to buy 4 domestic tickets. In the past, I know that I can use miles from one program to redeem ticker for another alliance airline. For example, I used Northwest miles to redeem Continental ticket in the past. With all the recent changes, I cannot keep up anymore. Is there a way I can check which Airline mileage program can be used on another airline?

You could go to the web site of each airline, they all list partner airlines that awards can be used on. Given the combination you have, you'll probably have to travel on at least 3 different airlines and meet up at your destination.