fswebcam
neat and simple webcam app
TLDR
Take a picture
$ fswebcam [filename]
Take a picture with custom resolution
$ fswebcam -r [width]x[height] [filename]
Take a picture from selected device(Default is /dev/video0)
$ fswebcam -d [device] [filename]
Take a picture with timestamp(timestamp string is formatted by strftime)
$ fswebcam --timestamp [timestamp] [filename]