I've gotten cups to work properly on 2 different desktops and 2 different notebooks using my method. Try it!
CUPS Slack9 Howto:
1.) Download the latest cups package from your favorite Slackware ftp mirror. You can find it in the Slack9/patches/packages folder.
2.) Install the cups package by doing:
# installpkg cups-version.tgz
3.) Reboot. You should see cups start with output "Cups scheduler started".
3.) Go to Linuxprinting.org. On the left side navigation bar, select The Database-> Printer Listings. Select your make/model printer, then click on the Show button. The next page will give you the option to generate a ppd file for your printer. Click on download PPD and save the file to /usr/share/cups/model. The file should be in a model.ppd format, if not, then rename it to my_printer.ppd.
4.) Restart cups by doing # /etc/rc.d/rc.cups restart.
5.) Go here and download the latest foomatic-filters.tar.gz (version 3.0 as of this writing). Then do the following:
# tar -xzf foomatic-filters-3.0.0.tar.gz
# cp foomatic-rip /usr/lib/cups/filter/
6.) Open your favorite browser and point it to http://localhost:631
7.) Under Administrative Tasks, add your printer. Just follow the directions.
8.) That's all there is to it!