A few years ago, I started a local chapter of freecycle, so I usually offer my used clothes on the freecycle list. It saves me time dropping them off at goodwill. Usually, I just let the list know the sizes, type of clothing, etc and set them at the curb. They are gone within hours to someone that can use them.
For anyone who hasn't heard of freecycle this is the web address:
The Freecycle Network
It's a place to offer ANYTHING you no longer want, so that someone else may reuse it, rather than throwing it away. You can also request items on the list if you have a use for items that people commonly throw away.