I buy most of my Canon gear at Adorama. Their selection is excellent and the service is great. They also give you the most money for used gear that you are looking to sell.
One way to get a really great deal is to search their “Refurbished by Canon” list of camera bodies and lenses. For example, they are currently offering a Refurbished by Canon EOS 40D body for $699 which is the lowest price I’ve seen for this body to date.
And you don’t have to worry about the condition of this gear. I’ve purchased several lenses in this program and they’ve all worked perfectly. Adorama includes a 90 day warranty to boot!