Small Business
A local small business can be a goldmine in terms of quantity of quality.  Furniture stores especially.  Few, very few furniture stores will throw practically new furniture out back next to a dumpster.  Your best bet is to drive behind as many furniture stores you can find in your area for a few days.  Don't act suspicious, though, or
they'll think you're casing the place for a robbery.  If you find a store that does throw away furniture, do not tell anybody.  When you go around blabbing to everyone you know about it and they take everything, don't say I didn't warn you.  Once the whole town hears about it, you're screwed.  As for other small businesses, you may or may not have to search through dumpsters, it varies.  If you do have to look through dumpsters, they're generally not dirty nor smelly.  They just contain cardboard, wood, things like that.  Just be careful not to get cut, or have the lid hit you on the head.  That'll ruin your day.