I cannot remember the brand name, but I once bought a converter for my printer that plugged into the printer where the cable normally goes, and the other side contained a port for an ethernet cable that you can plug into your router. It then provided an IP address for the printer that you can use for your entire network.
What ShadowAce is talking about is an HP JetDirect box. I have 3 at home that were retired from use in the company I work for. The plain vanilla JetDirect boxes are kinda hard to come by nowadays. Probably can find one on ebay for cheap.
The new ones all seem to be referred to as print servers and most have a bunch of bells and whistles that add to the price.
A quick search on the computer equipment website of your choice for "print server" will probably turn up something to fit your need and budget. TigerDirect has like 27 ranging from $25-$300+. Brand names are of little consequence anymore (it's all Chinese slave labor made) and you'll find a wide range of opinions here about which is best. Be sure to check the online reviews that almost all these sites offer now.