Other very useful tip I picked up when doing video manipulation the other day that deserves its own post is reencoding any video so that it will work on a vanilla Windows Media Player (without any other codecs added). Windows Media Player is probably the most stubborn, pathetic video player the software world has ever seen and unfortunately if you produce a video for the general public to view, you need to make sure WMP is happy to play it.
The tool for such a job is obviously ffmpeg, but the suggested commands on the compatibility page of their site seem to compress the videos to a horrendous state at the same time, so after asking on their IRC channel on freenode this is the command that turned up:
ffmpeg -i input -acodec libmp3lame -ab 128k -vcodec msmpeg4v2 -qscale 3 output.avi
Wonderful. Now I can render to whatever I please and worry about compatibility later.