Andy,
I have a Canon PIXMA IP3000 and Canon PIXMA MP500 (multi-function).
Both print directly to CD/DVD surfaces beautifully.
I think in The States most Canon PIXMA's do not ship with
the print tray and has a plastic insert blocking the tray slot. I think there
is some patent issue. Interestingly, I live in Australia and both came
with print trays and no insert.
The plastic insert can be easily removed and instructions to hand
build servicable print trays can be found on The Net or purchased
from eBay.
As far as software, I am a big fan of TurboPrint.
It is pay software, however is of great quality. It offers windows-like
control over the printer and has out-of-the-box Gimp integration.
I use Gimp to do the actual printing.
Regards,
AussieBear.