You'd be better off selling them on ebay to be honest. It takes more time and effort but you would probably get more for them.
If you don't have that kind of time, you will generally only get anywhere from a few cents to $3 per CD, depending on how recent of a release it is and demand, etc. Some stores that speciallize in selling used CD's/DVD's will generally have a set price, like $2 for every CD, $3 for every DVD, or something like that. I'm not so sure about clothes because I always either donate my old clothes or throw them away depending on condition.