Pannier for cannondale caad9? Every day I commute on my cannonade caad9 and carry a crumpler bag with my 15" MacBook pro, some work documents and often a change of clothes if it's a hot or rainy day.

After years of doing this I'm thinking it's time I started thinking about my back and am considering panniers for the commute. Yes a caad9 is a road bike and not so much a commuter, I also do road riding and prefer using the 1 bike for everything. 

Ideally it would be a pannier that could be very easily removed and be able to sustain the weight and clearance. 

Does anyone have suggestions on good kit to get for this?

Thanks!
Heelstrike, which Neil Fein mentioned in a comment, would be my chief concern. You'd need a rack that moves the panniers aft. Axiom makes just such a rack that is designed for bikes without rack-mounting eyelets—instead it mounts to your quick-release skewer (which could make changing flats a PITA). I have seen people touring on road bikes with these, so it can be done. It would also be possible with some racks to mount the rack to P-clamps at the bottom. They also make this clamp-on seatpost rack that supposedly has a 15-kg capacity. Should be more than enough.

You might also consider a large seatbag. This one might be too small and is spendy, but it seems like it's in the right direction (and if you haven't explored Rivendell's website, do so—neat stuff).