I've done some recent experimentation involving harvesting Canadian institutional repositories with the OAI-PMH protocol. Mostly this was a personal endeavour to determine how many there were, how much content they had, and how difficult/reasonable it would be to harvest them all and provide a search index. It seems that there's no comprehensive listing of Canadian repositories, so I had to gather and cobble my own.
It seems not to be a common practice for repositories to publish their OAI-PMH addresses. This is a minor tragedy. The list that I gathered follows for the edification of others who might have a similar need.
The list consists of 53 unique Canadian repositories, and where available, their OAI-PMH interface API's.
An experimental harvest (future availability uncertain) of these repositories resulted in over 367093 unique metadata records. The harvester used was an instance of the PKP Open Archives Harvester.
Updated July 4, 2012 to add Colonial Despatches