Like most of the others here, I use the Topeak Road Morph G pump. I typically mount mine under the top tube using the bracket that comes with the pump. On my touring bike I use Performance Bike's Hurricane ATB Extra Mini Pump Mount to mount the pump next to the bottle cage on the seat tube. The pump is exposed to a bit of road grime when mounted in this area, so you need to run fenders or make sure the pump doesn't get too dirty.