Well, if the shoes in question happen to be sneakers or athletic shoes of any sort, we take them to our local Nike store. Their Reuse-A-Shoe program is pretty great. They take used sneakers and turn them into surfaces for athletic fields (like basketball courts, tracks, etc.). They eventually want to recycle the shoes back into shoes.
If you live in an urban area and have a Nike store nearby, chances are you can just swing by and drop off your old shoes. Check, by searching for your hometown here.