This question is a bit old. But I think the answers, although they are technically right, they are misleading. Let me explain.
There is no direct relationship... but there are some indirect relationships, so they count.
The bridges on the relationship between Focal Length and Shutter Speed are:
1. The aperture
The aperture on a lens is a relationship ...
Actually, there is no relationship between them. Basically, the focal length is related to the lens and shutter speed is related to the camera sensor.
It can happen that you want to zoom (change the focal length) and your hands shake (or somehow the camera vibrates). What by zooming happens is that you are not only changing the focal length of the lens but ...