There are two categories, those that I know are pretty obscure elsewhere, and those who I just found out were Canadian in the past 30 min. Asterisks next to my top recommendations, bands listed in no particular order.
1) Sam Roberts
He's a new rock singer out of my hometown Montreal. Very up-and-coming. Songs to hear: Where Have All The Good People Gone?, Brother Down.
2) Ashley MacIsaac
One of my new favourites. He's a fiddler out of the Maritimes, does a wonderful mix between Celtic-type fiddling and rock-ish beats. Songs to hear: Sleepy Maggie*, The Devil's In The Kitchen.
3) Great Big Sea
Also a Maritime band with a Celtic/folk feel with a twist. Very upbeat and cool. Songs to hear: Mari Mac, When I'm Up I Can't Get Down, The Chemical Worker's Song.
4) Swollen Members
Canadian rap. I know, I can barely believe it either. It's the only rap I will actually admit to liking. Songs to hear: Breath*, Steppin' Thru.
5) Our Lady Peace
I'm sure even you guys have heard of them, they're so popular. Alternative rock. Songs to hear: One Man Army, Clumsy.
Edited to Add: *smacks head* I can't believe I forgot David Usher!
6) David Usher/Moist
Alternative band and the lead singer who went off and did some solo stuff. I think they're from Vancouver, but they live here. I get the impression that most of you guys have heard of him. Songs to hear: Breathe (Moist), Black Black Heart (David Usher).
I'll admit, I've heard only one song by him. But it rocks. And the video rocks. Very smooth, cool song. Songs to hear: Hang Ten*.
Fantastic cool alternative-pop sound. I listened to them with smar when we were in high school. Songs to hear: Someone Who Is Cool*, Make you Mad.
These guys are Canadian? No WAY. Okay, they're a weird band. Two guys from another band, The Philosopher Kings, created Prozzäk, which has two members, Simon and Milo. They're cartoons and personas, Simon is on the hunt for love, and Milo is a big dumb pretty boy who "likes to watch". You can check them out at the official website. Super poppy but very fun. Songs to hear: Sucks To Be You (possibly the most overplayed song of one year), Strange Disease (also a super-wide release), Wild Thing/Poor Boy (medley), Hot Show. I had trouble picking with this one.
I hope you guys try out some of these songs. Have fun!