I have a 5000 watt generator that I want to hook up to power my well and some lights and refrigerator for the next couple of days until power is restored. The generator has a 240 volt outlet which I have a plug and cable for. The cable ends in 4 wires: black, red, green white. The dryer outlet and dryer cable have 3 wires. I know that I would need to connect the white wire from the generator to the middle wire on the dryer cable and then connect the black and red wires to the other dryer wires. The question is, what do I do with the green ground wire? Should I connect it to the white wire?

Dangerous, no way to insure no back feeding. Cords may be safer.
Besides Transfer switches That select between Power Company OR Generator. Home Depot has small boxes that allows about 8-12 circuits the choice of either PoCo or Generator.
InterlockKit is one of the cheaper Faster, safer way to ensure safety:
http://www.interlockkit.com/