This is a good thread to start. I have found some AMAZING things in the local dumpster bins.
While I choose not to grab food, as usually there is a good reason to throw it out (packaged goods notwithstanding), I will list the various things I have found in the last 5 years below that have saved my stache some serious cash!
1.) 5ft tall cat tree (It had a few frays but was nearly perfect other than that. In the pet store, this cost at least $120 and in some places, even more brand new).
2.) Gamecube with Super Smash Bros and a controller (It was as if the trash gods had delivered the most amazing gift for saving real hard).
3.) A leather restaurant booth chair in pristine condition (just like the ones at your favorite sit-down restaurant).
4.) A corporate-style wraparound desk that only needed a few new screws and some elbow-grease to fix. Easily, this is worth $200 and I am still using it today (right now in fact, while I write).
5.) Wooden barstools for the kitchen (only minor scratches repaired with walnuts).
6.) About 200 sample bottles of Pantene shampoos and conditioners, thrown away at a CVS (NOT ON MY WATCH!)
7.) At the same CVS 2 weeks later, about 30 unused boxes of Colgate toothpaste that had just expired that week.
8.) Yet again at the wasteful pharmacy, 10 boxes of unopened Q-tips. I haven't had to buy any in years and still have 4 boxes left.
9.) A couple of wicker baskets I use for the bathroom
10.) A large mirror with a ding in the top right corner. I made a frame for it and now it hangs proudly.
During bulk trash pickup in my neighborhood that happens twice a year, I will go running around the neighborhood late/early and scope out the bulk trash. I picked up a sleeper sofa in perfect condition, minus 1 cigarette burn. (HELLO! flip the cushion over), an extra futon mattress for the futon when it started to sag a little, and about 40 golf balls that I drove into oblivion at the range, saving me a $10 ball fee.
I have no scruples about dumpster diving if someone else's trash is MY treasure. I will take it proudly, clean it up/fix it, and then use it until it is no longer practical.