Inspiration can strike anywhere, and if you're the type who needs to immediately write down their revelations, you might want to toss a few quid towards Brandon Saw who's Kickstartering a simple non-permanent adhesive wrap that turns any flat surface into an erasable whiteboard. If brainstorming is your thing, you'll want to cover every inch of your office in this stuff.
Like the plastic screen protectors that can be easily applied and removed from your smartphone, the Wrap feature a low-tack adhesive that keeps the material secured to desks, walls, and probably even ceilings, until you're ready to peel them off and take them down. And there are versions available for both wet-erase (easier to erase) and dry-erase markers (if you want to avoid accidental smudging).
The cheapest way to get your hands on the Wrap material is with a $15/£10 donation to Saw's Kickstarter, but that only gets you a few smaller pieces that can be slapped on a fridge. To cover an entire desk you'll need to donate at least $29/£19 for a custom-cut piece of Wrap, but the price can go up depending on the size of your workspace. Price-wise it actually seems comparable to hanging a whiteboard on your wall, but with the added convenience of it always being in reach of where you're working which seems to give it the advantage when it comes to usefulness. [Kickstarter - Wrap via Taxi]