Canon Support for Snow Leopard
http://support-au.canon.com.au/contents/AU/EN/8200620400.html
It looks like if your product is a few years old then it is not advisable to purchase 10.6, or be ready to buy a new printer.
As for their business products, such as the imageRUNNER series, none of the current Canon printer drivers work on 10.6. Having been involved with the 10.6 seed testing I found that while the drivers appear to install okay, the creation of a network printer queue fails. This occurred with the following drivers.
CUPS PS v2.11
PS v1.81
UFR2 v1.80
Fax v2.20
So if you feel the need to update, then beware.
If your Canon device supports PostScript, then you can use either the Generic PostScript included with 10.6 or install the Canon PPDs so that you get some finishing options.
If your Canon device only supports a Canon proprietary protocol, such as UFR2, CAPT or GARO, then there is currently no solution for them with Mac OS X 10.6.
Pahu
MacBook Pro 17', Mac OS X (10.5.8), Mac Pro, Xserve G5, iPhone 3G