K K.
Yelp
As Grisel L. noted, this hotel is not in the center of the action, but it is just off the Vondelpark, which is a lovely (and gigantic) green space with walking/running/biking trails, artwork, cafes, and an open-air theater, which happened to have live music the day I arrived.
My room was no-frills but lovely: queen-size bed, table and chair, end tables, a television, and a telephone. The bathroom was much larger than I expected, and the fixtures were nice and new. The hotel's quirk is that it's "green" and "eco-friendly," so there are little word balloons all around telling you about the hotel. For example, the table is made out of recycled coffee cups, and the countertop in the bathroom is made out of pressed paper. The bed has a medium-firm foam mattress that's quite comfortable. There's no artwork, just a large mural of a flower on the wall above the bed and a neat throw pillow depicting an old map of Amsterdam. There is also an elevator that goes to the first 5 of the hotel's 6 floors (the rooms on that floor are reachable by stairs). They don't give you little bottles of shampoo and conditioner (as that wouldn't be eco-friendly), so there is hand soap and a sort of shampoo/shower gel combo in the bathroom.
I did not try the breakfast (which is all organic) since it is quite pricey at 13.50 euro. Instead, I popped into the Albert Heijn supermarket just up the street and bought a loaf of raisin bread, jar of jam, and fruit salad - enough for my entire stay - for 4 euro.
Wifi is free throughout the hotel. There is a nice bar (both beer and coffee) on the ground floor near reception, with a wall full of plants, couches and chairs upholstered in funky fabric, and always buzzing with people.
The best part of this hotel? I booked online (a non-refundable room) for 65 euro. Far and away the best deal on a hotel room in Amsterdam I could find in early summer.