I was on vacation for ten days. When I returned I used the Echo to go to a store. It started well and I had no problem starting it to come home. Three hours later I tried to start it again and there was no noise at all except for the fan starting as well as the radio. I cleaned the battery poles- no go. I then jumped the battery with my other car and still no go. I do not hear a click nor does it turn over. What are the possibilities?

Possibilities are :
Starter itself (lately I've noticed they tend to go out quiet , with no warning) , Ignition switch , safety neutral switch .Check the starter first with test light.
Hook test light to small single wire attached to starter ,(not a havy duty wire) , the other end of test light to the ground , try to start the car , watch the light as you starting the engine :
Light on - starter is bad , Light off - ignition switch or safety neutral switch.(I don't think starter circuit has a fuse).

There is a "neutral safety switch" that makes sure the car is in park before it will allow the starter to operate .. there is also a safety switch on the brake pedal to make sure the brakes are on before allowing start .. .. if either switch is bad or misadjusted .. then it wont start .. you might try exercising those swithches a bit to see if you can free it .. operate the brake pedal several times and shift thru the gears over and over .. thats a nice little car ...