I seem to be stock piling used furnace filters, are there any uses for these things once the furnace is done with them? It seems a shame to throw them out; given that I change them once a month, there must be some way to prevent all this waste.

This might be a bit off-topic but the filters could be used in some DIY project, which would make it on topic. So slightly off-topic question, looking for on-topic answers.
EDIT:
Seems to be a lot of talk about changing the filter so often, here is an exert from ehow.com
Industry Guidelines The industry standard for any filter is to change once a month for the highest level of maintenance. Of course, this may or may not be necessary for all homes depending on their specific environment and how often homeowners use their furnace.