I have come across a need for url decoding as I got a link which was url encoded. And I have found a useful online tool which lets me enter a url encoded text and get the url decoded text. This also has functionality to url encode the given text. You may url encode as many times you want, but you need to decode the encoded text as number of times it was encoded.
I have found this as very useful for my purpose. And this works completely on client side. Please take a look at it.