Fancy taking in some hills? This goes one better than hill-reps. If I am not mistaken, this does not follow the same stretch of road twice (at least not in the same direction), but does tackle the Christmas Common from all directions. This route includes a tricky descent, see Ride-with-GPS for details.
I am a big fan of the Old Shed route on the Cowley Road Condors’ page, however, I prefer not to have to turn back onto myself. This route approached the Old Shed from the opposite direction. Look left, don’t miss it!