Yes, my current setup is that I have a Linksys 4-port router connected to the modem.  From that router, one port is connected to the Airport station that provides wireless connectivity throughout the house.  Two other ports are connected to two PCs through CAT-5.

It is possible for an Airport Station to serve as a bridge/gateway to both PCs and Macs because of the fact that it implements the 802.11b standard.  However, I tried to configure the airport through the PC and gave up after an hour of trying to get it to work with that.  So, I just used one of the Macs and configured the Airport station through the software that was provided.  After that, it was a piece of cake to configure.

So, all together, there are two computers that are wired to the router through CAT-5 and two other PCs (desktop and laptop) and two other Macs (iMac and powerbook) that have wireless connectivity through the Airport station.  Just as long as your gateway/bridge supports 802.11b any wireless NICs supporting this standard should work.  However, with the new 802.11a coming out, these two aren't easily mixed up together.