After some delay, I got this working. There are some gotchas' so I'll mention these for others who might have issues. The cupsd.conf file posted by two9er is basically good, but cups balked when I tried to restart it on my debian squeeze Plug. CUPS may be doing some transitioning. Seems like it anyway. I got it working by copying cupsd.conf.default to cupsd.conf and then altering that file with two9er's edits. The default file has several stanzas added to the bottom where the posted one leaves off. They are needed to keep CUPS happy, on my system at least. After this, things worked normally.
Again for others who might be trying to do this, here's the process I used.
1. Get the /etc/cups/cupsd.conf file properly set up as mentioned above. Do this first, since you
won't be able to get cups web access from your client machine unless you allow it in cupsd.conf
2. Maker sure your printer, usb cables etc are all attached securely and in good working order
It might be a good idea to check it all out directly attached to your PC/Mac if you haven't already!
If the hardware doesn't all work directly, you'll be endlessly frustrated! After getting #1 done, I had
a loose usb cable from moving the printer around. I caught it quickly, but it could have caused grief!
3. Use the cups web interface to add your usb printer to the Plug. Use http://IP-of-your-Plug:631
4. Go to the admin page and make sure that your printer will be shared
5. Print the test page after adding the printer -- that shows that printing directly from the Plug works.
6. Now you can set up printing on your local machine. There are several ways to do this...
7. I used "ipp" My local machine gets something like "ipp://192.168.5.87:631/printers/name-of-printer"
It's a good idea to use IP numbers rather than a name -- easier when guests come over w/laptops
You can go to the cups web interface for your client machine with: "http:localhost:631"
The ipp address is added there. The /printers/xxx part is a default debian printer queue.
Use the same name for the printer here that you used when adding it to the Plug.
If you use a Mac and add the printer there, the "ipp://IP-of-Plug:631" goes on one line
and "/printers/name-of-printer" goes on the second queue line. All should work now!
8. Its even easier on a linux client machine. The Plug printer was automagically discovered and easily
enabled. I didn't try it on Windows, but it should be fairly straight-forward as well. Several years ago,
though I had a problem getting WinXP to recognize a very old network connected laser-writer. I finally
got it to work by installing it as a "local" printer. So if your Win machine resists, try that work-around.