You should include in your list brochures that are left in shops.
I found out about the Ride to Conquer Cancer from a brochure/postcard I picked up at our dry cleaner. I've found out about most local organized rides this way.
In Edmonton, since everyone has to drive everywhere, radio might also be a good medium for getting the word out. I don't know how the cost compares to the other options on your list, but if you could get a few mentions during rush hour news/weather/traffic, that would be pretty good distribution.
Internet is a must, if not for first contact of an idea, then at least it's a place to go for details of the event.