Dirty Girl Gaiters
Dirty Girl Gaiters (http://www.dirtygirlgaiters.com/) are very breathable, non-waterproof gaiters made of Spandex. They attach by a hook to the laces and by Velcro to the heel. Dirty Girl Gaiters are available in many, many colors and patterns. They will keep debris out of your shoes and prevent laces becoming untied due to being snagged. Dirty Girl Gaiters are also very cheap ($15 + free shipping) and well made. If you've been to an ultra, you've probably seen Dirty Girl Gaiters, even if you didn't know what they were. Highly recommended!
In case you were wondering, I have the red DFL pattern:
If you don't know what DFL stands for, shame on you! If you do know, remember DFL beats DNF every time!