Hi this is my third picaxe project that has worked. Quick vid on youtube
two transisters amplify the mic send a signal to the picaxe 08m2 which then reads the first clap goes to a for loop and then checks every cycle for another clap before the loop runs out. If it reads another clap it jumps to see if the light's on or off and does the necessary job then returns waiting for input. There is another transistor used to up the current from the output of the 08m2 the relay needs 32.5mA to switch on. That was fun working that problem out.
The relay is switching 240 volts I bought a project box from ebay to house the workings and being 240v for safety as well. If you check out my other vids there is a breadboard version but works off a single clap or sneeze or cough so a lot of false triggering hence I opted for the double clap program
here is link for single clapper on the breadboard
I will post the code shortly as I have seen others looking for this type of thing and not much in the way of help coming forward so check back.