Agree that the LEDs from Pantera Electronics are a fantastic solution - they really do increase the brightness. There are also other creative ideas you will find to increase the brightness, if you search long enough, which mostly came about before the Pantera Electronics LEDs became available and folks had to use conventional filament bulbs. The dimmer switch often dies, I guess the windings burn out after a while. There is a quick and dirty solution which does work, all be it not as good as a new dimmer switch. This is to carefully inspect the back side and you will see what appear to be at least two cut off copper/brass coloured tabs (from memory). If you get your digital multimedia on them and wind the knob of the dimmer switch, you will probably see it works. Apparently there was a second set of windings that was not used. Then you just need to carefully solder on a pair of tabs, onto the 'cut off' stubs and voila, you have a working dimmer switch, probably... Worked for me on both my dimmer switches.
Cheers, Tim.