Or just screw a little 4 port switch to the wall in the nearest wired room and connect the cat5 coming from your main house switch (or router) to the little local 4 port. Then run a cat5 from one of those
4 ports to the nearest weak room. And you will have 3 extra ports available locally to hook up a peer-to-peer networked printer, NAS or whatever else to boot!My house is all hardwired but I only have one cat5 jack in each room, if need more than one wired port in a room I just get a 4 port switch and screw it to the wall next to the one jack. All the rooms are fed from a 16 port gigabit switch in the basement. That switch gets its IP addresses from my wireless router (connected to Comcast). I only use the wireless for laptops, everything else is on the wired LAN.
Bottom line is you dont need to home run another dedicated wire from the main router, just from the nearest wire available by splitting it with a local 4 port switch.
A 4 port switch costs about $20 more than a 4 port hub but will perform better and I think its worth it.