Cambridge Coffee is a weekly hang out for me. The environment is such that you can just chill out for hours on end. I often go, order my coffee and read a book for hours. They have tables and even a leather couch and chair to relax in (You will find me on the leather couch).
They have plenty of coffee, lattes and cold drinks to choose from, and some wonderful food items as well. My favorite latte is the Turtle Mocha. The quality of the beverages are on par with Starbucks, but the environment is much more inviting.
They also offer free Wi-Fi, so feel free to bring your laptop along and cruise the web. Often times, they even have a live music to enjoy.