Two doors up from Dark Horse Antiques, who had the cute pop bottles in their windows, is Flat Black Coffee Co. There is a guy that works there named Chris, and he makes the BEST iced mocha on earth. Flat Black serves mostly shade grown, fair trade, and organic coffees. They also have a number of delicious teas, which you can also buy loose if you'd like (I'm a huge fan of the Moroccan Mint Green Tea). They roast their own beans here at the Dorchester location, and if you're downtown and need an iced mocha fix, they have a second location in the financial district. They're opening their third location, also in Dorchester, before the end of the month.
You wouldn't think much about a coffee shop's windows display-wise, but these guys do a great job of decorating for holidays/season, and I think the coffee beans in the planters on their stoop are downright awesome. I love having an option of a locally owned, delicious product producing, creative, community involved company in my little neck of the woods!