Athithi, on Dwight - about a half a block east of Telegraph. This place is right up there with Vik's as far as authentic Indian food goes. Its cheap, its good and the people who work there are wonderfully friendly.
I've been three times in the past week, and each time I've had the lentil of the day, which is a bowl of spicy, filling stew for a whopping $2.50. I also usually get one of the appetizers - veggie squares are unusual fried patties of leafy vegetables and herbs - that comes with the owner's homemade chutney. The chutney alone is worth going for - it has cilantro, mint, and dates, and is far tastier than the stuff you usually get in Indian restaurants.
I fear this place will soon become one of those Berkeley landmarks with endless lines snaking out the front door - but it was just too good to keep to myself.