The first place I'd recommend is http://ebikes.ca, which is home to Grin Technologies, the best place I know of to get your ebike supplies--not because they're cheaper, but because they have great customer service to help you get started, *and* after you're already going (which you probably won't get at the cheapest places).
The second place, if you need help fixing your newly-converted ebike, or building one up from "scratch", or even just deciding what you want to get, is http://endless-sphere.com/forums, home to arguably the best source of DIY ebike information on the planet.
If you are the experimenter type, and would like to do this totally DIY, without using existing controllers, motors, etc., or you just don't have money to buy the stuff new, check out my older Electricle Project blog, where I worked out a couple of different bikes and drivetrains that worked reasonably well, before being able to get a more "normal" ebike motor and controller going on the second (custom-built) CrazyBike2.
More links and information to come as there is time.
