Now that Sugar Cafe closed (equaldistant from our home), we're left with only one great coffee shop in walking distance.... that would be Cannon Coffee.
Reasonable prices, decent brew, good small eats, and an awesome aura (complete with a back deck, local artisan sales, and open mic nights) make this the complete neighborhood coffee shop package.
Everyone is always nice and you get to see a great representation of the diverse neighborhood that is Brookline.