Amundsen Bryggeri n Spiseri - serves great mussels and their in-house brews are good.
Found Aegir Brew from Flåm at a random lunch stop in Grünerløkka while having grilled ribs.
Fuglen a.k.a the free bird, was another notable good coffee stop. Stockfleths may be a chain, but makes a very good espresso.
Just don't drink Espresso House ... taste like Starbucks to me.