I think I can help
I have Airport BaseStation and the following computers:
2 non-Apple PCs (windows machines, with standard 802.11b wireless networking cards)
1 Apple PC (with the Aiport networking card)
1 Printer (HP OfficeJet R40)
1 Print Server (HP 170X)
All machines can print.
The Airport and Airport Extreme will work with both Apples and non-Apples.
Let me explain the print server, because I had to buy it in order to get this to work the way I wanted it to and with little setup headaches. Also of note is that HP always officially maintained that my printer was for MS Windows and would not work with Mac OS X. Unofficially they built drivers for it and have a separate web address specifically for Unix/OS X/Linux drivers (another discussion).
"What is a Print Server?
Are you sure you want to know?
If someone told you that a print server was your average networking device, someone lied." [modified SpiderMan quote]
In most basic terms, a Print Server is a box that connects directly to your network via an ethernet cable or wirelessly. It then gets assigned its own IP address - that's the really cool part. The box also connects to your printer. Now on your computers, you will be able to add a printer using just the IP address - if you have a printer like mine, you'll need to download special drivers for the Mac, otherwise just setup your printer as you normally would.
In my case, the Print Server not only made my printer immediately available to all the computers on the network, it also supplied whatever the printer needed in order to work with a computer that wasn't a MS Windows computer.
I wish to reiterate that my non-Apple PCs have standard wireless networking cards for 802.11b. Which is the same standard as the Airport and is compatible with Airport Extreme (well, Airport Extreme is backward compatible - the point is they work together). You will be able to get standard wireless networking cards for 802.11g which is the same standard as the Airport Extreme. So you are covered on both non-Apple PCs and Apple PCs using either the Airport BaseStation or the Airport Extreme BaseStation.
By the way, setting up the non-Apple PC onto the Airport network was so easy, it's probably illegal in some countries...
Send me an e-mail if you would like to cover more specifics and trouble-shooting your setup, should you have issues.
Take Care,
Quark