You can try overexposing a bit (to make the flash put out everything it's got), but the reality is these little flashes just don't have much power to illuminate anything but with a directed beam. They absolutely need the reflectors and the lenses (fresnel) to focus the beam tight enough to defeat the inverse square law.
Picture a flashlight bulb in its reflector and out. The bounced flash is illuminating half a sphere, after ceiling absorbtion. Just isn't enough power to illuminate anything beyond 6-8 feet from the center of the 'bounce'. Even studio flashes get tamed by a 3' x 3' soft box, and they still have reflectors helping.
If you just can't get the distance you need, find a way of limiting the area illuminated by the flash. The wall+ceiling bounce can give almost a stop more than a ceiling bounce due to the quarter-sphere illuminated, and a corner bounce (tricky to do as the flash is typically shooting over your head, leaving your shadow on the scene) can give a stop more.
But the best trick is to get more than one flash going. Porters, and I suppose everyone else, sells those cheap little photo flash triggers that fire a flash when they see one. You can buy some cheap, dumb flashes each with a light trigger, and position them strategically (or is that tactically?) around the room to light up the ceiling and walls. The trick is to get the slave flashes nearer the subject than you are, without making the scene look harsh. (Having a digital camera or polaroid to see the overall effect is a very handy thing while setting up.) One method: put a slave in each table lamp in the room pointing at the light bulb. That way of you include a lamp in your shot, it looks normal (and the lamp acts something like a modeling light, previewing the effect for you). Please note that you'll need to take your camera off full-automatic mode to keep the exposure right (unless you have a EOS 3 with multiple 540 flashes, all controlled by the camera). Multiple-flash setups is why they have flash meters.
Get some old Kodak How To Take Pictures books. They are full of stuff like this.