On commercial flights it often feels like the plane is gets faster just before touching down. What creates that sensation?
The aircraft flares just before touching down. It descends with a constant velocity, and just before touching down pulls the nose up to reduce the descent. This results in a higher angle of attack, more lift, and a vertical deceleration of the airplane. A passenger perceives this vertical deceleration as a force. Direction of the force is straight down and the aircraft is nose up, you're leaning back, so there is a component of (gravity + vertical deceleration) that pushes you into the back of your seat.
This same effect is used in flight simulators with a motion base. Upon accelerating, the simulator pushes forward like the aircraft does, but also slowly rotates backwards so that the pilot feels sustained seat back pressure. He cannot see the leaning back angle inside the simulator because the horizon of the projected outside visual image does not move. As happens in the aircraft: look forward in the aircraft and your view of the inside of the aircraft is always the same, irrespective of aircraft angle.
So for your eyes there is no apparent tilt, the inner ear senses rearwards force, and there is increased pressure from the seat backrest. The brain translates this into perceived forward acceleration.
Visual perception of your perspective; as the aircraft gets closer to the ground your field of view constricts and you are closer to terrain and other structures, making them appear to move faster past the jet than at altitude.
I think what you're feeling is the brief float due to the ground effect. Within about 10 feet of the ground the air being forced down by the wing encounters the resistance of the ground. It actually arrests the downward motion unless the angle is pretty steep and that float gives a slight sinking feeling that feels like acceleration. Sometime too the pilot will add a little throttle to transition out of the ground effect a little less abruptly.
As the plane descends into ground effect, it may actually accelerate if the engines are producing enough thrust, since in ground effect the plane requires much less power to keep "flying". Power from the engines will translate into speed, if not height.
I don't know if it happens often in real world landing configurations, but it's certainly possible. To make it happen for sure, set the power so that the plane is just barely descending, and when it gets into ground effect, it will certainly speed up measurably.
when the flaps are lowered more power is applied to make up for the losses sometimes I fell a drop in speed and then a little surge in acceleration.
It does accelerate just before touching down in case something goes wrong with the landing gear and the plane has to immediately take off again.