Sonarca Sound Recorder is a straightforward tool for recording sound input to WAV or MP3 audio files.
The program is easy to set up. Choose the input device, and the specifications of the output file (mono or stereo, bit resolution, sampling frequency and so on) and that's just about it. You can then just use the large Record, Pause or Stop buttons to start and end recordings as you require.
Alternatively, you can also tell Sonarca Sound Recorder to automatically stop recording after some defined period of time, perhaps useful if you won't be around and don't want to leave the recorder running indefinitely.