I would not think of going to Amsterdam without going to my favorite, the Pancake Bakery. Interestingly, for Americans anyway, it doesn't open until noon. A great lunch for two would be to split a savory pancake e.g., ham and cheese) - they're big enough for two - and then split a sweet one (e.g., banana with whipped cream!). http://www.pancake.nl/

There is also a pretty good pancake restuarant in the park across from the Heineken Brewery too, but not as good as above.

Another place I like - though not authentic, but tasty and very fun is Rosie's Cantina, for Mexican. Always jammed.