Hooray, my field of speciality!
The router shouldn't care a damn if you're running Windows, MacOS, Unix, Linux, whatever since it'll be configured to run TCP-IP and be configured by either a platform independant web browser or through a telnet session. Since Macs can access the internet quite happily they are obviously configured to run TCP-IP and read HTML, so no problems on any of those accounts. If your aim is purely to share internet access then no problems.
Buy yourself one of the bigger name routers and you should be alright, names like Linksys, DLink, Netgear, even Belkin are ok for most things. I've configured quite a few in my time and while they all have their idiosynchracies they all do pretty much the same thing and have similar setup systems. They will allow you to share your connection, give out DHCP addresses and block ports and incoming attacks. No home should be without one.
If you get one then you might as well spend the extra couple of bucks and get a wireless one, wireless adaptors for PCs and Macs are pretty inexpensive and getting faster all the time. You'll generally get a speed of about 30 Mbps out of a wireless link between computers, even though they claim up to 54 Mbps you'll almost never see that speed. If you need more speed between your computers then go wired by running CAT5 ethernet cables with RJ-45 ends (RJ-11 is the smaller connector used on phones/modems). This will give a stated 100 Mbps but again dont expect that actual speed, and then only between your networked devices, not the devices to the internet. If you dont pass massive files between your computers then no need for wiring.
The only thing with going wireless is the security issue. It's usually an easy matter to put on WEP encryption, but I personally also make sure I only allow my PCs MAC addresses access and dont use DHCP so that no other PC can join my network even if they crack the WEP code. From my house I can pick up 3 other wireless networks, one of which is unsecured, so best ensure you put on security.