CNCzone is one area to get informations.
But Google is also a big source.
Here some of pages I have found and used
http://www.hobbycnc.com/
http://www.pminmo.com/my-diy-cnc-wood-router
http://buildyourcnc.com
I have look into build one - and as I understand, it is possible to build a "small" one for 500 USD, without the Router and the PC
The PC has just to be an old one, one there are normally possible to get for free, the software you can get for free, if you can live with the limits there are in the free version.
And then you need the router - you don't have to starte with a Festool, it is possible to start with Dremel or one of the cheap copies, I have seen them i DK for around 15 USD on sale.
I think this guy have some great idears
http://www.solsylva.com/ - I have paid the 24,95 USD for the 25"x25" machine and get the delivery by mail (about 2 minuttes after I have paided).
I find the plans very good to get some idears from.
And I paid 140,00 USD incl Post and Packing for the three motors, controller and powersupply in China. This was an Nema 17 motors if you what to have a more powerfull motors the cost around 80 USD more.
Here is a guy the have build one complete for 700 USD
http://www.hoddo.net/cnc.html
/Per