Nuremberg is a city in northern Bavaria
You can quite frequently find stuff in the streets. Often next to the glass-dumpsters bunches of furniture are growing. Dumpster-Diving is possible. There are also different local networks about sharing.
There are a lot of supermarkets in nuremberg. Some of them have their dumpsters not locked up.
for example, Visit Aldi in Adam-Klein-Straße, Zara-Markt in Fürther Straße
You can also always try to ask small turkish vegetable-shops to give them their trash. For example, when you show up in the very early morning at 6 at the Plärrer-Supermarkt, they often give you tons of stuff.
Another possibility is to go to the Market on the Hauptmarkt after its finished. That should be around 15h...
An insane possibility to get the craziest gourmet-food ever is to dumpster-dive the Bio-Fach organic-food-fair. Actually you don't even have to dive in the bins. just go through the exebition-halls, and take what they give you! You have to show up the last day and bring a bike-trailer or even a car... You may be have to buy a ticket... Its once a year in spring.
other food possibilities
Go to the Futterbombenbande in the Projekt31. The adress is An den Rampen 31. Food is distributed for free to everyone. Mostly bread and sometimes Vegetables and fruits. Its every Monday and thursday at 18.30 (At the same place is also a freeshop and a vokü!)
One is in the Projekt 31. They have lots of clothes and several other stuff. 
You can also try the umsonsttheke Its a shelf build out of fruit-boxes where people can leave their stuff, they don't need anymore. It is in the Kirschgartenstraße in the tunnel under the red house and accessible to everyone. (it just got destroyed a little bit... may be someone will build it up again.) Or you try the Umsonstvitrine (the same thing in plexiglas) at Wandererstraße 81
The jesus-freaks in the Rothenburger Straße in the "Nordkurve" have also a freeshop. Its only open on Saturday Mornings.
Rock im Park
This a enormous Rock-Festival at Dutzendteich. (It takes place on the former Nazi party rally grounds, which is a bit sarcastic...) Anyways you can get loads of useful stuff there when it is over. People leave really everything behind them. You can find entire tents, all kind of camping-seats, sleeping bags, clothing, well just anything you would take on a festival. And there are also tons of not even opened bottles of alcohol. A lot of people go there, also to just get the deposit.
The Quellkollektiv will soon (summer 2016) open a kind of second-hand construction-store. All kinds of materials will be collected and can be taken against donation. You may also use the workshops.
At the recycling-station in Fürth, you can get stuff from the bins. Electronic devices, wood, glass, whatever. You can even call them and ask them to keep a certain kind of stuff for you.
If you want to have piles of bright grey cardboard, go to meier-kartonagen in the austraße. You can for example draw on them.