Actually, there are several ways in which to network equipment, including the existing home telephone lines and powerlines within the house and the technologies have been around for many years.
You can do peer-to-peer networking between computers, or get a router or switch & network the computers together and setup "sharing" so they can all use the printer when attached to another computer.
You can also get a print server to attach the printer into the network:
http://www.wisegeek.com/what-is-a-print-server.htm
http://www.newegg.com/Store/SubCategory.aspx?SubCategory=387&name=Network-Print-Servers
http://www.google.com/products?sourceid=navclient&rlz=1T4HPIC_enUS309US255&q=print+server&um=1&ie=UTF-8&ei=yNzwSvndOJOANojmyIoH&sa=X&oi=product_result_group&ct=title&resnum=1&ved=0CCUQrQQwAA
Here's a link about home networking in general & the different options:
http://books.google.com/books?id=dvepQ3QRe3gC&pg=PA17&lpg=PA17&dq=telephone+line+networking&source=bl&ots=twwc_mBiAL&sig=wyQyG2-k0zmLJipDeUwSBtqglJM&hl=en&ei=cM7wSon4N4rOsgPFkdz0BQ&sa=X&oi=book_result&ct=result&resnum=8&ved=0CB8Q6AEwBw#v=onepage&q=telephone%20line%20networking&f=false
Here are links for telephone line networking:
http://computer.howstuffworks.com/phone-network.htm
http://www.homepna.org/
http://www.homenethelp.com/network/phoneline.asp
Here are some links that explain sharing and setups:
Microsoft site that explains how to setup and share your printer over a home network using XP and another web site that explains it a little differently:
http://www.microsoft.com/windowsxp/using/networking/expert/honeycutt_july2.mspx
http://www.pcstats.com/articleview.cfm?articleID=1596
Best of luck.