Resources for Art Supplies
Whenever possible buy your supplies at your local art supply store. You want them to stay in business. Not only will you be able to run down an get a tube of paint or canvas or brush at the last minute, you can also learn a lot from those that work there. Get on their mailing lists so you know when sales and other special events are taking place.
But when you can't or don't have a store nearby, here are some USA websites that have a broad selection of products. Some of these also ship to Canada:
In Canada: