If you live in a hard water area, like I do, you probably have problems with limescale. I know that it builds up very quickly in our house so I try to deal with it on a regular basis, particularly in regards to the kettle. Limescale won't actually harm the appliance but it doesn't look pretty, and I'd rather keep my kettle looking its best for as long as possible rather than having to replace it purely because it gets a bit ick.
Fortunately, de-scaling a kettle is one of those household jobs that only takes a couple of minutes of your time. This is what my kettle looked like before its most recent de-scaling. The build up gets particularly bad around the lid.
First of all, I tackle the inside of the kettle. To do this I mix one cup of white vinegar with one cup of water and pour it into the kettle. Leave it to sit for one to two hours, or overnight if the limescale build up is especially bad.
I deal with the build up around the lid by soaking small strips of paper towel with neat white vinegar. After a couple of hours the limescale literally wipes away with no effort.
Before using the kettle again, make sure that you rinse it out thoroughly with water - you don't want your tea or coffee flavoured with a hint of vinegar! And here are the shiny after pictures: