D.O.A., formed in 1978 and based out of Vancouver B.C., is certainly one of the most influential Canadian punk rock bands. Their music is an interesting mix of political and party punk. They even have their own hockey team. I've seen them about a half a dozen times since moving to the Pacific Northwest and I've never been disappointed.
Here's a short history and release list of the band.
Here are a few streams and Mp3s.