I've recently put my order in for Thompson & Morgan
(www.thompson-morgan.com). It's pricey but full of rare stuff. In
the past I've ordered from McFayden's (www.mcfayden.com) and have had
good service. Would also like to mention Eternal seeds and Seeds of
Change (www.seedsofchange.com) for heirloom vegies.

Here's list of other vegie sites:

http://www.seeds.ca/library/rl/rl.htm