How to make blurred effects?

[paulscode]

What would be the best way to simulate the blurr effect that happens for super-fast repetative motion (such as a hummingbird's wings)?  It doesn't seem like a billboard with alpha would work in this case, since it isn't the same shape from every angle. 

Anyone have experience with this?

[EgonOlsen]

I've seen this effect on helicopter blades. It was simulated by a simple, blurred texture, i.e. the motion blur was baked into the texture.