Just came across this question while trying to connect a webcam. If the webcam encapsulated audio that is fine. But what if I want to attach a microphone in another location / locations.
Question: How can I record audio using a microphone?
There is no microphone input in the Raspberry Pi. Raspberry Pi's sound chip only supports audio output, not input. If you want to record some audio using RPi you will have to use some external microphone device, like USB microphone. Some USB webcameras also have build in microphones so you could use it.
You can either use a USB sound card or a GPIO header based sound card, such as the ones mentioned here.
By location, if you mean a different sound card, try using audacity and it will allow you to select the recording input device.
If you want to record in different locations (with different Pis), perhaps you can stream them over the network ? Using something like the rtp from ffmpeg (avconv).