Situated right near the Stockholm T-bana Slussen stop is a humble food cart called Nystekt Stromming where you'll find delicious and filling Stockholm street food at very affordable prices.
I stopped by here on a Friday night and got a huge plate filled with fried herring, homemade mashed potatoes, lingonberries, creme fraiche salad, dill mayonnaise and crisp bread, all for the extremely inexpensive price (by Stockholm standards) of 75 Swedish krona. It might just be your best deal in the city.
Swedes love herring. They can happily eat it for breakfast, lunch and dinner, and it makes an appearance on all the major holidays. This humble street stall on Södermalm serves terrific herring in a variety of ways, from freshly fried to wrapped in bread to go.