Just be wary of which bag you leave out. I have heard of unscrupulous (did I spell that right?) people trying to get you to leave your unwanted clothes etc out for charity, they then collect these and proceed to 'Ebay' your goods for their own profit. I have heard that some of these people actually go and collect bags that are official charity bags ahead of the rightful collection. In short in order to be assured that your goods are going to real charitable organisations take them to your local charity shop personally or ask a friend or relative to drop them off for you.
HTH