You will need to first decide how large you want your whiteboard to be. For the purpose of this instructable, I will focus on the size that I built, but all the dimensions are flexible. Take a look at the drawings and the measured SketchUp file attached below for the details. You will need the following materials:
Two 4 x 5 foot sheets of white tileboard
One 4 x 5 foot sheet of 5/8inch plywood (I used 3/5" MDF, because I had it around, but it is heavy!)
Four 8 foot long 2x4 inch studs (you will cut this into 4 6-foot lengths, two 2-foot lengths and (optionally) four 1-foot lengths cut at 45% angles)
Four 4.5 inch long, 3/8inch bolts (The length of the bolts will depend on what you use for the center of the boards.)
Four 3/8inch nuts (if you are careful in your measurements, you might be able to get away with acorn nuts, but getting that to work is tricky, even though it does look nice!)
Eight 3/8inch washers
Eight 1/4inch lag bolts (I actually used some little furniture assembly threaded inserts like this
to make it easy to take apart, but I couldn't find them at Hope Depot, so you can use lag bolts instead.)
(optionally, 16 2.5inch drywall screws)
You will also need some basic hand tools:
A drill. Make sure that it is big enough to work with the large-sized bits that are used in the project. A good electric drill will probably work fine.
Drill bits: At minimum, you will need a 3/8 inch drill bit, 1 1/8 inch bit, and (depending on how you attach the feet) a 1/4 inch bit. You will also need a means to countersink the fasteners on the feet- I used a 1/2 inch spade bit, but you can use a Forstner bit or a countersink bit if you have one - I don't.
A pair of wrenches in the appropriate sizes. I used a ratchet set and an adjustable crescent wrench.
Measuring tools. At minimum, a measuring tape and a steel rule. A framing square or something similar in order to make sure that cuts are square.
Saw(s): I did all the cutting with a circular saw, using a crosscut blade for the 2x4s and a composite blade for the rest. If you are not cool (as I am not) an don't have a table saw, you can also use some straight steel angle-iron and clamps to provide a guide for your saw.
You will need a screwdriver to match any screws you choose to use. I needed a regular philips one for the drywall screws that I used.
A couple of clamps, preferably ones with soft non-marring jaws. I like the ratchet-action bar clamps from sears.
I also used a couple of sawhorses that I borrowed from a friend (hi, Pete!) in order to make it easier to do all the cuts. The MDF that I used as the center of the board made a dandy table before I cut it, too...