As a DIY'er - this place is a sanctuary. I've been here quite a few times during the weekends .. if not to buy .. just to browse around. This place is huge and you can pretty much find anything. If you can't find something you're looking for - you can simply ask one of the CJ personnel making rounds to make sure you've found what you're looking for.
I was looking for a bi fold door few weeks ago and found exactly what I was looking for less than $15. - you can find doors as low as $5 and I'm not talking dirty stained or broken door. Besides used goods - there are few new "recycled" items including plastic corrugated roof panels and paints for super low prices.
Also, if you're remodeling your house and need to throw those old materials - they have a number of recycle bin where you can simply drop it off.