This page is dedicated to non-commercial links which may be of interest to gardeners. 

With your suggestions, this list will grow.

Canada's plant hardiness map provides insights about what can grow where. It combines information about a variety of climatic conditions across the entire country to produce a single general map.

US Department of Agriculture
The PLANTS Database provides standardized information about the vascular plants, mosses, liverworts, hornworts, and lichens of the U.S. and its territories. Canada is covered to some extent.