Below is a list of different methods that I would recommend for creating your own whiteboards. With each, you have a list of advantages and disadvantages. The methods are broken down by use; you have different needs if you want one large whiteboard instead of twenty small whiteboards.

This is not a list of all of the different whiteboard materials. Most commercially-available whiteboard surfaces that come to the consumer as ready-to-use whiteboards are not listed. Below are only things that may need some sort of instructions in order to make a whiteboard properly.

Laminate

If you laminate tagboard, you can create fairly good dry erase boards without spending loads of money. This would work great for teachers who want each student to have a whiteboard, or if you want a cheap whiteboard to keep track of figures at your desk. I have used them while playing D&D to keep track of turns and my hit points during battle.

Pro: It is quick, easy, and cost-effective.
Con: When marks linger for a while, they may stain the plastic. It is not as easy to wipe off as a real whiteboard.
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The method is simple: Just find some tagboard and laminate it. You may need to find a local copy shop or a school to get it laminated with one of those nice industrial-strength laminators. I have heard of bad results if you try to use some types of clear contact paper or a similar sticky plastic as a laminate. You want to find the type that is melded together by heat under a roller as a press.

MB4000W Whiteboard Coating

This is similar to a clear paint and is sold by Solutions MB. It is quite durable and easy to apply. It almost is exactly the same as some high-quality boards, and almost everything wipes right off. It would be ideal for coating walls of a room, resurfacing a whiteboard, coating your desk or table, and making any sort of solid surface into a whiteboard.

Pro: It can cover large areas and turn them into a whiteboard surface. Can keep the original surface's colors and designs intact.
Con: There is a little preparaion you need to do in order to have this product stick properly, but the process isn't hard and is totally worth it. Also, tiny lines and miniscule bubbles may form just because you are applying it with a foam brush or roller.
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First, you must prepare the surface. It is best to work with the surface horizontally if possible. They recommend you first coat your surface with a matte or eggshell, latex-based paint base. You do not need to use white. I used a rose colored pink. It's possible to get the paint base before they add color to it so you can apply clear paint and preserve your original wall colors and decorations.

Wait for the paint to cure, not merely dry. This could take a week to be safe.

Now you simply use a foam brush, roller, or other really smooth way to apply the MB4000W coating. It doesn't take much. You can even go over it again after an hour or two to generate a thicker coating. Now you need to wait at least three days for the layer to cure, but then you are able to doodle on your wall, use whiteboard markers on the table, or be artistic wherever you applied the coating.

Plastic Sheets

Some plastic sheets work well as whiteboards. To use them, you just need to unroll them or put them on the table. This may work well for covering a desk or table, having a portable whiteboard, or if you want a small whiteboard for your wall.

Pro: Inexpensive and quick to set up.
Con: Marks may stain plastic. Sometimes stays rolled and is hard to flatten.
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Well, the setup for this is easy. You can cut the plastic sheet to fit your surface, or mount it on the wall. I used a clear sheet that looked like a window shade and hit id underneath a drape/valance thing.

Contact Paper

Contact paper is readily available at most major stores. It is quick to apply and you can get some nice designs. Try for ones that are very glossy, usually cheaper contact paper is better. This is good for making individual boards, and coating small desks.

Pro: Cheap and easy to find.
Con: Markers left on can stain, contact paper eventually peels away from surface.
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First, cut the contact paper to fit and then peel back a corner. Apply the corner to the surface, making sure it still lines up properly. Slowly peel away more and use a flat edge, such as a credit card, to push the contact paper onto the surface. Make sure to go slow and get rid of any air bubbles right away, since you will not be able to remove them later.

Polycoated Cardboard

Realtors may use a special cardboard for their signs, and you can usually pick up similar materials from a sign shop. Test a sample first. These can make great personal-sized whiteboards and can be obtained for next to nothing if you can find a good source.

Pro: Typically inexpensive and usually work pretty well.

Con: May be hard to find, may have advertising on the back. Markers can stain surface.
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These babies are the simplest of all to make into whiteboards. First, you can cut them down to the size you want. Next, you're done. See? Easy!