I second the Mucinex. Works great. Also look for this stuff called Airborne. Helps keep you from getting sick on airplanes, etc.

On the sinuses thing...When I flew to Brazil, I had a terrible head cold and severely clogged sinuses. After take off in Miami and take off and landing in Brasilia, I was about to behead myself I was so sick from the severe sinus pain. I figured that I could do one more landing in Cuiaba, but I wouldn't be so fortunate. Because of bad weather, we were diverted to the next stop. From there, we flew the plane's regular route making several take-off's and landings at airports several hundred miles apart before finally landing at Cuiaba. I think we did about 8 take-offs and landings. I don't remember much of the last few flights since I was in such severe pain. They had to help me off the last flight.