From Photojojo (click here to read more)

The magnetic bulletin board: huge, affordable, and so easy to make you just won’t believe it.

What You’ll Need

* 3 x 4 sheet of galvanized steel — ours was about $14 at the Home Depot, in the same aisle as the siding and roofing material
    * Pencil
    * Ruler
    * Drill and 1/4Åç or smaller bit
    * Piece of scrap wood
    * Hammer
    * Small nails or screws
    * Assorted magnets
    * Lots of beautiful photos

Note of caution:
Be really careful when handling that big piece of sheet metal—the corners are sharp and the edges won’t do you any favors either. Wear gloves if you have them.

Also, this project won’t work if you get aluminum by mistake. Bring a magnet with you to the store — if the magnet don’t stick, it ain’t steel.