I am a big fan of Tinto, and try to make a point of visiting whenever I am in the Roncesvalles area. This Latin American cafe specializes in quality organic and fair trade coffees, and is also just a wonderful place to spend a peaceful afternoon.
One thing I like in any coffee shop is their ability to offer milk alternatives like soy, and unsurprisingly Tinto delivers on that front. They don't really even have a menu up to speak of, other than a board with specials. If you ask for a coffee-based drink they can likely make it, and if not they can probably come up with a suggestion of something else they can make based on what you like. There are usually a number of baked goods on offer as well, although in my experience the coffee is the showpiece.
The shop itself is very well-lighted, with big windows providing a lovely natural light source. The seating is also more plentiful than you might expect and generally comfortable for settling in with a good book. The shop and the people running it also seem to be very involved in the surrounding community, and as such they support, hold and advertise many local events, especially those relating to the arts. Overall a great place with a relaxed vibe and a no-worries attitude (no one pushing you to buy or get out).