The Color Run: Such a cool idea! Run a in a white t-shirt and by the end of the race you're not only covered in sweat, but lots of pretty colors to hide it! :P If only the locations weren't so far away.
Impossibly easy to make-DIY waterproof homemade race pace band- takes less than five minutes to make. Link to a template for both marathon, half marathon, and in miles or km. These are a must if you want to stay on pace during a race.