An adequately sharpened pencil
Piece of string at least 16" long
Staple Gun and staples
Box of 3" and 1 5/8" screws
Circular saw or Chop saw
Sanding device (I used a Metabo Compact sander with a rough sanding stone and 220 grit sandpaper)
Two sheets of 3/4" plywood 24" x 24" (~$6 from Home Depot)
4' of 4" x 4" (7' piece ~$7 from Home Depot)
12' of 2" x 4" (7' pieces ~$6 from Home Depot)
24' of 2" x 6" (8' pieces ~$6 from Home Depot)
12' x 1' of outdoor carpet (~$19 from Lowe's)
36" x 9' of rubber carpet padding (would've been $38 from Lowe's, but it had a couple holes and I was given a half-off discount, schyeah!)
4' x 4' of vinyl fabric (faux leather, you can get it cheap by the yard from a fabric distributor)
Since I already had all the tools I needed except for some screws, this instructable cost me approximately $90, which is by no means cheap, but if you search for them online they sell for anywhere from $250-$400.
Note: When completely finished this sucker weighs....a lot. I would assemble it where you plan to use it, and if you absolutely need to move it, turn it on its side and roll it. I am not responsible for any bodily harm including hernia, constipation, rug burns, or shattered expectations resulting from performing the outlined steps or while using the mushroom. Play safe.