Wired = Yes. Just run a wire from one routers WAN port (making sure to set it up to be in Dynamic mode, and set the routers IP 1 digit off of the one it's getting connecting to) to the other routers ethernet port.
Wireless = Sometimes yes, sometimes no. It all depends on the router itself. In my case the SMC router has what's known as a "repeater" function. This enables it to talk between different wireless routers wirelessly. It will essentially repeat any wireless calls it receives to the other wireless router.
For that Linksys WRT54GC router check out their site
HERE. It has instructions on how to set it up as a repeater. I can't recall exactly, but I believe that you will have to setup that router as the repeater, and have the W11 be your main one.