I'm addicted to Mojo. Even though it's frozen yogurt, I'm always happy to walk four blocks in the winter to get some.
They have delicious flavors that rotate frequently (which can be a bummer if you get addicted to something seasonal) and a huge variety of toppings.
It's possible to get a small bowl for less than $3, since they charge by the ounce. Make sure to get a frequent customer card, after you collect 10 stamps you can get a free bowl of yogurt. Also, follow them on Twitter (@MojoYogurt) because on Tuesday they post a code for 50% off your yogurt that day.
Overall, one of the best places on Mill for a treat.