About two minutes ago. Rattled the whole building for about fifteen seconds. Wife also felt it out in Scarborough (about ten miles away). Just in time for the G20!
From the comments: felt as far away as Montreal.
PS. Still not up on U.S. Geologicao Survey website, but I am hearing around 5 or 5.1.
PPS. Details here. 5.5, epicenter North of Cumberland, Ontario. Out of country visitors to this blog (I've had about 1,000 total in the last half hour) may feel free to blame Canada.