Turns out that it wasn’t MoviesForMyPod that wasn’t working, it was me. As you can see in the illustration (click for a better view if you can’t see it) there’s an option to select Windows Media or Quicktime as a playback option.
I had switched this to Quicktime, but never refreshed the page so it was still full of .asf files. That didn’t even matter, since I spent most of my time trying various freeware programs on an .asf file I had downloaded last week.
While revisiting unitedstreaming yesterday I noticed that suddenly all the files were using quicktime suffixes because by now Firefox had refreshed.
So unitedstreaming works better than I ever thought it did. I feel silly for not noticing this before, but at least now I can put a lot more video on my iPod to show my students.