I have been thinking about putting a sign up on our door requesting no hawkers/charity collectors/leaflet drops/whatever for a while now. We have been getting these leaflets (more often than not without bags) in a constant stream for quite some time now.
On a slightly different note, we have had to stop answering the door unless we are expecting someone to call, as every single day without fail at least one, if not more, people arrive on the doorstep asking for sponsorship/donations etc. for random charities, many of which I've never heard of. In one evening alone we got hit for over €20 (ok, all to reputable charities) between kids asking us to buy raffle tickets, sponsorship for the mini-marathon, collections for local sports clubs, etc. We now don't answer our door and will wave gaily out the window at the collectors instead.
Back on topic, if I spot a charity clothes leaflet being pushed through the letterbox, I tend to walk straight back out and ask the person to either take it away with them as i have no clothes for donation (not to them anyway) or throw it in the bin in full view of them. At least that one leaflet-dropper will know the next time not to waste the walk to our front door.