calgary metal just off blackfoot and ogden road used to carry stock on square and round tubeing.... if not any more they are a metal recycling place and have lots of pieces you could sift through for cheap. I know i buy alot of recycled aluminum stuff there, usually companys just drop of old stock they dont want anymore.
Russel Metals has been good to me in the past, but they have a minimum order amount, do depends on how much you need. I think its $250, don't quote me on that though. They will cut to length and have lots of stock, their prices are lower. Metal supermarkets if you need a small amount. Let me know what you are looking at for a sled deck project, I have one you could look at if you need. Fired you a PM.