A friend referred me to Dr. Loren Wilson at North Cambridge Dental Associates a few years ago and I have since referred almost too many folks to mention.
Dr. Wilson is NICE. He offers reduced rates for teachers, and doesn't charge you for your check-up (just the cleaning) if you don't have dental insurance.
He's not trying to sell you anything. I have grooves in my molars that another dentist called cavities and tried to get me to fill. Dr. Wilson said as long as I brushed regularly, they'd be fine. Four years later, they're still fine.
He's a good dentist. I've had him replace one filling, and have no complaints. I have another friend who had serious work done on his mouth -- I mean SERIOUS work -- but still gives Dr. Wilson rave reviews.
He'll go out of his way to accommodate you. His assistants will call you before an appointment to make sure you can still make it -- and will persist in calling until you call them back to confirm that you can. But if you're trying to get an appointment, they'll also call and let you know if an appointment frees up.