Found the kitchen floor covered in water when I got up in the night, around 4 am. Immediately googled emergency 24-hour plumbers, only to find that the five or six I tried did not in fact answer their phones. Because I grew up in Leaside, eventually decided to give Leaside Plumbing a try... success! The owner himself answered the phone, and committed to having someone at our house first thing during business hours - 9 am.
The plumber they sent, Keith, was great... he diagnosed the problem under the sink, and also fixed another problem with the water heater in the basement. We needed a new faucet, and he advised us to give him a call when we'd bought one, so he could arrange to come back and instal it. Fortunately we were able to get one within a couple of hours, and he came back toward the end of the day and installed it.
Can't recommend this company highly enough - from start to finish, and in the course of a few hours, they solved our problem as well as a potential future problem. Tom, the owner, was friendly and efficient (even though I'd awakened him in the middle of the night!), and Keith was knowledgeable, customer-oriented, and very pleasant to deal with.