I'm planning in using my web cam as a security cam at my front door and I was thinking in using a pc downstairs to see my web cam over the net, but I have keep both pcs running at the same time and the need of extra software as well, so i decided to use a Cat5 to run a Usb connection over at least 25', I've been searching a little over the web and I found a couple of ideas to connect Usb peripherals over Cat5 successfully and I went over the subject, but I realize that i didn't want to cut the cat5 and solder the usb connections to the cable, so I decide to build a couple of Usb dongles (female and male) to cat5 and the cool thing is that they can be used on existing Ethernet network wall connections as well. I know that I might be pushing the limits but it's worth the try.
I wouldn't use this devices for Data tho, I understand the there are plenty of connectors out there that have baluns (which I don't quite know how they work), to send and receive Data signal, so I wouldn't risk the try but for peripherals such as web cams, mouse or keyboard, and sound signals would do just fine (even S-video).
I would highly recommend using a powered Usb hub for the distance mentioned above, in regards of some of the limits for this type of configurations:
Usb limits are up to 15' (4.5 meters)
S-Video up to 50' (15' meters)
I got very useful information from Tony's Cafe blog, on distances limits and some other valuable info, you may want to take a look at his site: http://girasoli.org/?p=58
Step 1: Materials and Instructions
2 Ethernet Hubs (8pin RJ45 - salvaged from network cards)
1 Usb Male Plug Type A (any standard Usb cable)
1 Usb Female Plug Type A (from a Pc)
Solder Gun, wire and electric tape.
and of course a CAT5 Ethernet Cable
The hardest part was desoldering the Hubs from the salvaged PCB board, after that it was just a matter of selecting which cables of the CAT5 use to solder the Usb plugs and the RJ45 Hubs.
I select the pins in the following order:
RJ45 hub = USB plug
pin No. 2 = Green Cable
pin No. 4 = White Cable
pin No. 6 = Black Cable-Ground
pin No. 8 = Red Cable
I test the configuration at the other end and test the web cam (my work very well) later I isolate each soldered connection with electric tape (with yellow tape) and cover the hole thing (black tape), and voila!. 25' of video cable (plus the hubs) and working.
Easy and extremely cheap.