We dumpster dive, although haven't been doing much recently as int he summer a lot of our spare time is spent on the garden.
Anyways,we've done retail dumpsters as well as residental. Residental had produced a lot of really nice things.
Retail has been hit or miss, sometimes find a full dumpster of stuff, soemtimes nothing but empty boxes. Make sure you check your local laws on the legality of it in your city and surrounding cities.
I've posted this in the past I think, but here are some pictures of stuff we found last winter, we haven't added to it in a long time.
http://www.flickr.com/photos/1421215...7603884031586/
We've found cash, Books (sell in Half.com) gold rings (cashed them in for $200 in cash at a jewelry place that buys old gold), brand new tag still on Columbia jackets and duck boots (they fit perfect), tv/ vcr combo, bullets, food, beer, wine, rolls ands rolls of new garbage bags, coke/ pepsi points, baseball cards and other collectables. A bike frame we found last winter just sold for $50 the other day on Craigslist, we could have cleaned it up and sold for $200, but didn't want the bother. My favorite PJ pants came from a dumpster as did the desk I am sitting at right now.
You can check out the forums at dumpster world, but beware as the IQ seems rather low in there and they are not friendly to "newbies". The general age of the poster seems to be about a 15 year old male teenager (they are older, but that's the mentaility), but you can learn some stuff by reading the old threads. They also talk in code about actual stores, but it's fairly easy to figure it out. If you do post on that forum don't ask them about the local laws in your area as they will rip into you. Don't ask for ideas, they will rip into you. On rare occasion a serious and mature conversation will occur but it's infrequent...
The biggest thing you need to do is get out there and look. What else?