A few days ago @chiah tweeted a link to a video from iBusinessMagazine demonstrating how to make a $4 wall-sized whiteboard.  Since I have recently been debating paying $150+ for a whiteboard for my home I decided to give this a try.

The local Michael's arts and crafts store had everything required:

- 1 roll of Clearphane by Highlander $10
- Dry erase markers $7.50
- Eraser $2.00

Total w/ tax ~$20

Yes, this is a bit more than $4, but worth it in my opinion for the reasons listed next.  This solution is inexpensive, easy to setup, and convenient.  However the real benefits are surprising.

Pros:
- Great way to test "Do I want to spend $150 on a real whiteboard for my house, office, etc.?"  Use this for a week or two and see how much (and in what ways) you actually use it.
- Could be setup for gathering in non-office location: (insert name of)Camp, strategy session, etc.
- Party.  Let guests exchange ideas (since so many of parties become brainstorming sessions anyway) or simply draw.
- Giant Canvas. This is the real hidden value!  This creates a HUGE canvas upon which to create HUGE art. Or a lot of small art.
- Children. Those with children (or guests with children) can do the bottom of a wall and let kids be creative w/o worry.

Cons:
- Massive glare (difficult to take a picture of anything but a small area
- Certain colors show better than others (blue, using EXPO brand markers)
- Occasional issues when writing/erasing across border/overlap
- Erasing after marker has set a few hours requires some effort
- If you have pets, vacuum first.  There will still be hair under the cellophane anyway.
- Bubbles/ripples will remain even after smoothing that will be visually distracting, but won't interfere with writing too much

Installation tips:
In addition to the video, here are a few extra pointers to improve the process.
- After laying each strip, use the tube to smooth out air.  Slide sideways first in one long motion, then diagonal to top and bottom.
- If laying multiple vertical strips for a writing surface higher than 3 feet, lay the bottom strip first.  This creates a clean 3 feet high writing surface and decreases the likelihood of crossing the border between two strips.  When laying strips close to the floor (for use by children, for example) lay the top strip first, then bottom.
- If laying multiple vertical strips, allow overlap between the strips.  Creating a perfect line for the two strips would be difficult enough.  The danger or pulling or ripping the material when drawing or erasing is much greater than when strips overlap.  Also, overlapping strips will stick to each other.
- Be careful putting tacks in, as the pressure will break the seal with the wall and pull the material towards the tack. 

Will I use this as a permanent whiteboard?  No.  Will I use it in situations listed in the Pros section? Yes.

Here's a (low quality) pic of a mind-map on my $20 wall-sized whiteboard.