A lot of Lexmark printers work with the z600 driver, which unfortunately is not offered by CUPS. It is pretty minimalist but the printer does print acceptably. I have copies of the two required files in Slackware tgz format, which are easily installed with installpkg. If you'd like them, send me a PM with your e-mail address and I'll e-mail them to you.
The scanner part of the Lexmark needs its own driver. I have an X1270. The printer part works with the z600 driver. The scanner part did not work until the SANE driver came along with VL6 and finally the scanner would work. However, it is not a good driver, as it puts faint vertical bands in the scan. They are not there with the Windows driver in XP, so it's not the scanner. With VL6 SOHO the driver seems much improved and it doesn't show bands.
There are drivers for many Canon printers but they're hard to find. They are issued by Canon. Likewise for the scanner part. Canon had a driver for my Pixma MP160 but now there is a driver for it in CUPS. I'll look into it tomorrow (if I remember) and tell you what I find. The Canon software for the scanner works well. It's called scanimage or something like that. I'll check that out, too.