Barn in the Sticks offers great products to squirrel proof your bird feeder.  Use products like Cole's Flaming Squirrel Sauce or Squirrel Away to mix with your regular bird seed.  They contain a punch of pepper, which birds don't mind, but squirrels will hate.  If you have a bird feeder on a pole, Squirrel Slip is a food grade oil gel, which when applied to the pole, will make it tougher for the squirrels to get a grip and climbing up the pole won't be so easy.  We also have new bird feeders from great American companies like Droll Yankees to keep the squirrels out.  The Yankees Dipper, Flipper, Whipper and Tipper will also give you the fun of watching the squirrels being safely thrown to the ground after being thwarted from your birds' feeders.  We also have caged bird feeders, which allow small birds to get in, but not squirrels and will also deter larger birds like grackle.