Amazon.ca is the Canadian arm of Amazon.com. The .ca site doesn't have all the bells 'n whistles the .com has, but it's still ahead of other book etailers in terms of features. Prices are competitive.
Canadian Amazon.com shoppers are limited to books, CDs, and DVD/video.
Prices are competitive, customer service is exemplary, and shipments to Canada are timely. They've been around a long while, and have their routine down-packed as a result.
They've got the biggest customer base so products are more likely to have customer reviews at Amazon than anywhere else which helps immensely for purchasing decisions - no matter where you end up purchasing the item.
Did Juju mention the customer service? Best customer service on the net -- all the other etailers should take lessons.
Chapters.indigo.ca is the result of an Indigo takeover of Chapters in early 2001. Huge inventory. They're the big boy on the Canadian online block when it comes to books.
Zip.ca is an online DVD rental site that lets you have 4 DVDs out at a time for $24.95/month. No late fees or shipping costs. They claim to have "over 18,000" titles available.