a) get an *analog* video camera, they're often pretty inexpensive. Feed the NTSC video output over coaxial cable over to an inexpensive video capture card in the PC in the next room.
b) get a cheap PC like the $75 Intel ATOM motherboard + CPU (both included) from newegg, stick in one of the $22 sticks of 2GBy RAM and find a $25 case + PSU on sale to stick it in. Use a normal USB webcam with that. Advantage: you can have a quiet cool running PC on 24/7/365, and it'll probably save you money over the months in electricity bills anyway. Added bonus -- if you run one of the LINUX based webcam surveillance programs on it it'll more easily do things like motion detection and enable easy remote access for your review if you're out of the house like a webcam-over-the-web or sending snaps to your cell phone / via email or whatever. Consider if doing continuous webcam capture will interfere with your use of your normal PC, what the energy use cost of leaving it running will be, whether it will likely crash often in this capacity, whether good free capture / video processing software is available freely which will meet your needs for it, et. al.
c) get one of those wireless RF modulators and a camera that outputs NTSC video and then you can send the signal wirelessly to the next room, though coaxial cable would be better.
d) USB cables can be daisy chained through multiple hubs. MAYBE if you got 2-3 cheap AC powered USB hubs and some 15' or however long is reliably available USB cables you could get the string of them to be long enough to put a USB webcam into the next room. Potential problems with data corruption / flaky operation / electrostatic discharge / tripping over the cables exist.