I have been using Network Redux's shared hosting for about half of a year now without any problems for what it is worth. They have much larger packages as well but I cannot speak to those of course. They also support open source software projects financially. http://www.networkredux.com/
There was Bryght, which was the first hosted Drupal solution. They were based in Vancouver, subsequently purchased by Rain City Studios. They've since shut down the service.
Groups.drupal.org is a part of the drupal.org group of sites. Logging in on this site requires an account on the main drupal.org site. If you do not have an account on drupal.org, you will need to create one, log in over there, and then come back here where you should automatically be logged in.
Network Redux
I have been using Network Redux's shared hosting for about half of a year now without any problems for what it is worth. They have much larger packages as well but I cannot speak to those of course. They also support open source software projects financially.
http://www.networkredux.com/
DRB
http://resume.danielbaer.com/
There was Bryght, which was
There was Bryght, which was the first hosted Drupal solution. They were based in Vancouver, subsequently purchased by Rain City Studios. They've since shut down the service.
http://raincitystudios.com/blogs-and-pods/scales/the-end-of-a-bryght-era
As far as I know, none of the other services out there are based in Canada.
Acquia is working on a hosted solution ("Gardens"), but I don't know much about it, or when it will be available.