Best Frequent flyer miles program?

[Tenchuu]

I was wondering if any of you have experiance with these things. My work routinely flys me accross the US and i get to keep the miles but I need to get this some frequent flyer program started and was looking for suggestiosn from peopel with experiance

btw mainly use Alaska, horizon and US air.

[P4rD0nM3]

Mine's on Northwest airlines. Every round trip that I make rounds up to another round trip so basically, it's almost free...but I've been a member ever since the wheel was invented.