Among the different kinds of edible berries that grow wild in Norwegian woods are the cowberry (or lingonberry - called 'tyttebær' in Norwegian). These are sour-tasting but make wonderful jam (a favourite relish together with reindeer meat, beef etc.) . The best way of preserving the fresh fragrance of these berries is simply to add sugar and stir, then keep in a fridge or freeze down. The photo shows cowberries picked in the woods near Oslo in 2009.

Picking lingon berries in the forest (using a picking scoop)
Picking lingon berries in Nordmarka

Below is the result of two days' colletion of lingonberries and diverse fungi in the forest some miles north of Oslo.

The jars contain lingonberry jam, the freezer boxes 'stirred lingonberries with sugar' (rørte tyttebær)
Fungi collected in forest near Oslo

The close-up shows mostly 'porcini' fungi
Porcini fungi collected near Oslo

Below is a close-up of saffron milk fungi plus 'piggsopp' (Hydnum repandum) and 'brunskrubb' (birch bolete Leccinum scabrum)

Below are lingon berries, piggsopp (top left) and region cantarelles (traktkantareller)
collected north of Oslo on September 15, 2014 - (with homemade Prince cake i.e. fyrstekake -top right)
Funghi from Nordmarka
Below - piggsopp in close-up. Pigger are spikes (underneath the hats)

In marshy wooded areas, one find the most prized (and expensive) Scandinavian berry, the cloudberry or 'multe' (Rubuschamaemorus L (Rosaceae family) - light yellow in colour and much like a loganberry in appearance, but a bit smaller and having a more distinctive taste. They are eaten like raspberries and are also made into jams, preserves and even liqueur:-
Cloudberries (multer)

Region cantarelles (traktkantareller)
traktkantareller i fleng

Another favourite in the Nordmarka woods is bilberries:-
Bilberries in Nordmarka

And of course, wild raspberries
Wild raspberries in Nordmarka woods, near Oslo

Below is fungi collected in the same area some years ago
Edible funghi collected near Oslo

By contrast, the red fly agaric fungus - known in Norway as 'rød fluesopp' is not for your normal cuisine. It can be eaten, however, if one thinks one might like the psychotropic results, including hallucinatory experiences. Presumably, it does not affect its main consumers negativelty, i.e. the flies that enjoy it.