61B is a great spot for delicious coffee. Surprisingly, the smoothies/juices are freshly made (with actual fruits and vegetables) and absolutely delicious as well - I usually go for a smoothie to avoid being tempted by one of the huge cookies that look equally amazing.
I've sat and done work there a couple of times, and the atmosphere is quiet, bright, and pleasant. I especially like that I don't get that 'coffee shop smell' that often permeates my clothes at Coffee Tree Roasters...