There are quite a number of good mountain bike areas within a 1 - 2 hour drive from downtown Toronto. Carl's MUni trials photos. Kelso has 16 km. of hiking and mountain biking trails including connections to the Bruce Trail. In addition to 36 km rolling ski trails, they have an additional 45 km of challenging single track trails. These trails have been designed and cut specifically for those who want a more technically difficult ride.
Helmets are mandatory.
This will be the site of the Mountaining Biking events if Toronto gets the Olympics in 2008. Here are some photos from the 24hr event that was held there. It's on of the largest 24hr events in the World. 400 North to Barrie - take the 400 extension north of Barrie. Take the first exit off the 400 extension onto Forbes Rd.