One-port wireless?

I have a Linksys 4-port router, but I want to connect a fourth computer that is too far for CAT5.

1. Is there a way to make just one of those ports wireless?

2. Can I connect a wireless router to the fourth port, so I don't have to buy wireless network cards for every computer?

 

You can get a wireless bridge to plug into your wired router, but most wireless routers (even the really cheap ones) have a 4-port switch built in. The cheap linksys I am using right now does, so do many of the D-Link and Netgear routers.

 

Get a wireless access point (WAP) to plug into the 4th port on the router. Linksys, Dlink Netgear all produce WAPs. Leave all your existing wired connections as is; add further PCs by giving them wireless cards. Wired and wireless will all work together just fine.