HD quality with the rear camera of the Samsung Galaxy S2 and also record in a much lower (but still very acceptable) quality with the front facing camera, but what if you just want to record the sound?
Firstly you will need to find the "Voice recorder" application, this will be in app drawer and look a bit like a microphone. In the screen shot to the right it's the the Green icon with a large black "microphone" on it (don't confuse with "Downloads").
After opening the app you will need to press record then speak into the microphone. You can use the controls on the bottom of the screen to stop the recording, pause it or even cancel it with ease as will as the "equaliser" style display at the bottom to show how loud the recording is.
Whilst this this may seem like a rather pointless application it does have a number of notable uses. You could for example use it to record something like a university lecture (as long as it's loud enough), your own thoughts for a sound-style diary (or a "Captains Log" if you rather) or just record yourself singing for a youtube video with out needing to do your make up. The options really are there and you could well end up finding yourself using this more than you may first think.