Trev's suggestion was excellent. Look through the oil fill cap and make sure that the cam is rotating when you crank the car, or better yet, pull off the distributor cap and watch the rotor to be sure it turns. I don't recall what the distributor drives off of, but I think that it is an idler shaft that is cam-belt-driven. If so, failed timing belt would mean no distributor rotation and no spark signal.

Low-probability - there is also probably a roll key that locks the drive gear to the distributor shaft. I saw a V-6 Chevy loose its roll key once. The mechanic (who worked in the bay opposite mine) almost went crazy trying to figure out what was wrong.

If both valves happen to be stopped in the closed position on the #1 cylinder, you would hear air rushing out (and in) through the open spark plug hole when you were cranking.