I wouldn't dive into a dumpster but I in my summer job I dismantle cars in my city's wreckers' yard. Near, like 20 meters from it is a recycle center which collects pretty much everything from electronics to paints to batteries to plastic, you name it.
Every now and then, ignorant people bring in their old videogames that "their son doesn't use anymore". We made a deal with the nice man in the center that I'll dismantle whatever his old Opel needs and he gives me me all the old computer and videogames he receives.

Well, it works like magic, last summer I got about 50 NES games, some MD games, a Dragon32 computer and a lot Commodore stuff among others.