There are lots of good foam cutters and DIY boards. For the boards look at http://www.pminmo.com/ For a simple foam cutter, just stay away from the drawer slide designs. They aren't that much cheaper than going with a bearing set up. Look for groups on groups.yahoo.com. Look at http://tech.groups.yahoo.com/group/CNCFoamcutters. MACH 3 by Art at http://www.machsupport.com or http://gm.cnc.free.fr/en/index.html or http://foamwork.net. This should help you get started. I have a firend that has designed and built a hotwire heat controller and I will see if he will give out the plans and get back to you.
If you are like me and most everyone else that gets into this, you'll get the bug and find yourself branching off into all sorts of neat CNC things. ALso, if you build it all from scratch, you'll know a feeling of real accomplishment when you first hook everything up and press a button on your PC and things move the way you hoped they would.
The web sites I've listed above are owned and operated by the designers, builders, and writers of their products. Great support as well.
If you need motor sources I have a good source for those as well. http://www.kelinginc.net Good prices and support. What else is there?
Good luck and have fun.
I am not affiliated with any of these sources nor do I buy for anyone other than myself. Don't be afraid to ask questions of the various vendors. There a couple of people that want to sell but I've heard bad things about after the sale support.