I've found a lot of questions on the internet on how to record the sound and video at the same time from the webcam. Here's the magic incantation that worked well for me (it assumes you do not have any video capture devices besides the webcam and already have one ALSA soundcard besides the mic of the webcam - if not, adjust accordingly). This is a single long line:
mencoder tv:// -tv driver=v4l:width=320:height=240:device=/dev/video0:fps=30:forceaudio:alsa:adevice=hw.1 -ovc lavc threads=2 -ffourcc xvid -oac mp3lame -lameopts cbr=128 -o recording.avi
EDIT: with a purchase of the Sony Playstation Eye camera, the above does not work all that well at all - at the high rate my mencoder misses too many frames. Something I found that is a bit better:
gst-launch v4l2src ! 'video/x-raw-yuv,width=640,height=480,framerate=(fraction)25/1' ! mux. alsasrc ! audioconvert ! 'audio/x-raw-int,rate=44100,channels=2' ! mux. avimux name=mux ! filesink location=test.avi
This lacks the compression, and the voice is a bit dragging compared to video - but gives more or less the 30fps that the webcam sends.