Despite its name, The Laundromat is anything but. This cafe has a high energy vibe, great food, and (my personal staple) coffee!
On Austurstræti, just a short walk from the main shopping district, it's a perfect place to stop and refuel. It can get a little loud, so don't go expecting to have an intimate dining experience, but they do have free wi-fi (just ask for the password).
I tried a lot of restaurants in Reykjavik, and this one came out as one I actually went to more than once.