North by NorthEast is one of the premier music festivals in Toronto. It features hundreds of artists from a plethora of genres, across a large number of venues. It's the companion festival to Austin's South by SouthWest.
For the musician it's a great chance to interact with peers, sit in on panel discussions, meet industry insiders, and play for a usually enthusiastic audience. For music lovers its a great chance to see about 20 bands over a weekend.
First week of June - For more info, check out their website here.