Here is a link to a new style of lockwasher we are looking at at work. They are better than split washers and nylock nuts.
The salesperson has a vibration stand that shows how clamping force goes down with vibration using the other types of locking devices. These Nord-Lock washers actually increase clamping force when they loosen.
I have not used them on my bike as of yet but plan on it when Fastenal starts stocking them at work.
http://www.nord-lock.com/