There are many ways get snapshots from your videos. Please add your favorite! You can also get audio from your videos.
With gxine Edit
One simple way is with gxine. While it plays a video, you can save a frame with Ctrl-s. For example:
$ gxine monkey.mpg <<video opens in new window>> <<Use Ctrl-s to save a frame>>
If you pause the video and use the position slider, you can more accurately grab the exact scene you want.