If there are two things I love about the BK-based blog Brokelyn, it's their attractive staff and ability to spot great deals in Brooklyn. Most recently, they've brought us a list of coffee shops that offer discounts if you bring your own mugs or reusable cups. This is great because A) discount! and B) it's better for the environment and C) you don't have to scoff at a barista who spells your name on the paper cup as "Flergen." Here are their Park Slope recommends:
Red Horse Café
497 6th Ave., between 13th St & 12th St., Park Slope
Discount: 25 cents off drip coffee with your own mug.
Various Brooklyn locations (in Park Slope, 7th Ave between Garfield and 1st Street and the one inside B&N at 7th Ave between 5th/6th Streets)
Discount: As part of their Green Project, they take 10 cents off beverages when you use your own reusable travel mug.