Rather than a router, I would use a hub, anymore, they are getting cheaper and smaller to the point where it would fit nicely on a 5 1/4" bay and you could easily run cable to the back of your case and have the ports on a pci bay cover. Also, thinkgeek.com sells a pci card that does what you looking for that can be found here http://www.thinkgeek.com/computing/accessories/5ad1/
Mobile-2.2Ghtz Core 2 Macbook, 4GB ram, 160GB HDD
Server-Dual 1.42 MDD G4, 1GB ram, 4 random hard drives.
PC-C2D 2.4Ghtz, Asus Commando, 2Gb ram, 3 hdd's in raid 5, 8800GTS.