In writing my last post, I came across an excellent plugin that allows you to insert a video from MSN Soapbox, Google Video, YouTube, MySpace Video, Yahoo! Video, muveeMix, and myvideo.de. This plugin is extremely easy to use, but it does require you to know the URL of the video ahead of time.
As you can see, you have a lot of formatting options when inserting the video and can modify everything except the link after it has been inserted. The plugin also provides an options dialog where you can set default options.