How to keep the squirrels away from the bird feeders

Well, since I hung most of my feeds on the laundry line I haven't seen the squirrels that much.  But when using the pole as a mount for my other feeders this simple and free trap works wonders. 

Just take a 2L pop bottle, cut off the bottom where the bottle's shape reaches full width.  Be careful not to cut yourself.  I used a box cutter to do it.  Then do the same to the cap of the bottle, so that the opening slides over your post.  Cut it to wide, use electrical tape to hold it in place on the pole. 

The squirrels will climb up the pole and have to go into the pop bottle opening and it doesn't get them anywhere. Of course the location of the feeder shouldn't give them a chance to jump on the feeder from a taller object like a fence or a tree. 

Here is a picture of it on my feeder containing the nuts and sunflower seeds. As you can see, this is also where my other "laundry line feeders" hang in the summer on the left and the right.  So that pop bottle is extremely important to have out here in the woods.  We also have lots of chipmunks.  The other deterrent we use is our Dog. ROFL.  She lives for chasing these critters before they even make it to the pop bottle. 

Any other solutions and suggestions are always welcome.