I bought a very expensive digital camcorder years ago, and one of the best – and least expensive – investments I ever made to protect my camera was to buy a UV filter.
The UV coating on the filter helps to reduce the amount of ultraviolet radiation reaching the lens when I’m shooting outdoors. This is very important of course; if the lens ever gets ruined, there goes the camera.
For about ten bucks, it’s certainly worth it, and I recommend that you buy one if you don’t have it already for your camera. It’s cheap protection and you can certainly leave it on your lens all the time. That way you don’t have to worry about cleaning your lens or blowing off dust particles too.