Damnit, I kept meaning to reply to this thread and then kept forgetting.
I have no real logical progression to conditioning. I'll pick standard distances and weights (50' distance, 100lb keg, stuff like that), but after that my goal is always the same; generate maximal misery. I'll usually figure out my conditioning workout as I'm getting my implements ready, thinking to myself "what can I do with these things to really make life suck today."
The better my conditioning, the crazier the workout gets.