You can add additional switches, both to the back of the router or daisy change them as well.
I recommend connecting lower bandwidth hogging devices to the switches, and devices that use more bandwidth, connect them directly to the back of the router or on a switch that is mainly used for high bandwidth Internet connections. Try to separate higher traffic devices from lower traffic if possible.
Heres my set up:
ISP Modem>Router->24pt Switch<>All wired devices here. PCs, Boxee Box and File Server.
-><xbox gaming consoles wired to back of the router. I could put the boxee here however we don't do a lot of Internet streaming with it, mainly stream from the File Server.