All the links in the central list below are personally recommended.
Pandora An internet radio station based on the Music Genome Project. Input an artist or song that you like and it'll give you one with similar musical "genes" which are identified by a team of professional music analysts. I don't envy their job, but it's a pretty good way to discover new music.
Soulseek A filesharing program that focuses on indie and artistic music. This makes a good combo with Pandora. If you really like a band you download here, the classy thing to do is support them: see them live, buy their album, or do both at once so more of the album sales go to them.
Pitchfork Media A good source of updates and information for the worldwide indie music scene.
The Beat Goes On Hunting for used CDs or DVDs in Canada? Keep a list on this site and they'll email you when one comes in.
Rotate This The best indie music store in Toronto, and more importantly, a handy ticket outlet.
Stillepost A forum for music discussion and local show listings across Canada.