First, playing video (and audio, for that matter) has worked out of the box much better with 11.04 than with previous versions of Ubuntu. I play my Guatemalan radio station and CBC audio and video without having to fool around with any setup.
To make videos, I loaded up OpenShot.
sudo apt-get install openshot
That didn't install ffmpeg, which has been my main fallback tool. It seems to be the tool that does everything, although as a command line tool, I find I usually just cut and paste an example command line from the Internet. It's not that I'm afraid of the Linux command line. It's that I don't know anything about video. So:
sudo apt-get install ffmpeg
That seems to be all that was needed.