I'm looking to take a single SkyHD source and distribute it to three TV's in my house. I've heard this can be done over CAT 5/6. Can anyone advise to how this could be done? And could I network these TVs to make them become monitors for an internet feed?
An expensive solution to your problem
first costs $2000 but you can get it on Ebay for less:
This lets you display the same source on 4 screens. (allows you to switch between 4 sources).
The other one is a matrix solution and costs $4000, allows you to watch a different source on each screen (and control the source). Note you need 2 cat5 cables per screen (one for Audio/video and one for the HDCP signal if the source is using this).
as for PC - just get a graphics card with a DVI output, connect it with a DVI to HDMI cable. Should work fine.
The final option is sky multiroom (£200 per sky box plus £120 per year) which is considerably cheaper.
Cheaper Option at the End of the Year
According to the latest issue of T3, the Slingbox Pro HD will be out at the end of 2008, and if you couple that with a Slingcatcher, that should do what you're looking for.
Or try out Smart-E
www.smart-e.co.uk do solutions for switching single/multiple video signals over Cat5 network cable. Not sure on the cost, you have to email them for a brochure (usually this hints at expensive ;) ).