Smear Crisco all over the windshield!!!
just kidding, but some suggestions from http://www.wikihow.com/Stop-Windshield-Wiper-Blades-from-Squeaking
1. Clean the windshield glass with a product like Rain-X or Windex so that the glass will slick up and the wipers will glide more easily.
2. Replace your windshield wiper blades often.
3. Refill your windshield wiper fluid.
4. Make your windshield wipers softer by putting a little WD40 on a paper towel and wiping the squeaking wiper blade with it.
5. Sprinkle baking soda on a dry paper towel and rub it on your windshield's glass. This will remove any wax or other squeak-causing residue from your windshield.
6. Clean the windshield with phosphoric acid (Coke) on really hard cases by letting it sit for a few minutes then rinsing it off with water.
7. Check to see if your blades are too loose or too tight. This could be causing tension between the glass and wiper.