Thanks for the input. I looked at the jockey wheel, and there seemed to be some dirt in there so I tried to clean it out. That helped a bit, but it's not perfect. On my ride in to work this morning, the chain slap was still there. With the chain still attached, I spun the rear wheel and it moved the pedals, I believe that's also an indicator that the free hub may need to be cleaned and lubed too.

At what point should I worry about getting the free hub serviced? I live in the Pacific Northwest, where it is pretty wet and the roads can get pretty gritty with run off from the hills.

Thanks!
Brad