The next time you host a brainstorming session, take notes on the wall. IdeaPaint can transform any wall into a dry-erase board. Start with a coat of primer, then apply a layer of IdeaPaint. A $200 kit, available at IdeaPaint.com, contains a roller and enough paint to cover 50 square feet, for a cost of $4 per square foot. By contrast, whiteboards usually cost $8 to $20 per square foot.