http://www.heise.de/ct-tv/
has a SWF9 video player that doesn't work.
It only shows a white rectangle

(file #18572)

http://5min.com also doesn't work (SWF9).

Videos also don't work at http://www.filmroster.com

It looks like it's going to start and shows some controls, but then just sits there forever with no video or audio. 

I don't know how to determine whether its a SWF8/9 site.

as of this year, gnash now supports youtube videos pretty well.  however, the same statement can't be made for most other flash video sites.  i've compiled a list (in no particular order) of sites that are currently not working:

http://video.google.com (videos will sometimes say loading, and some will play sound, but none show images)

http://www.hulu.com (the frame of the video player loads, but it says "unavailable")

http://www.thedailyshow.com/full-episodes (just get a black window)

http://www.southparkstudios.com/episodes (spiral spins forever)

http://www.cbs.com/innertube (just get a grey window)

http://www.ebaumsworld.com/video (videos play with sound, but audio skips and gets out of sync)

http://vids.myspace.com (just get white window)

http://www.cnn.com/video (frame loads, but neither video nor sound starts)

http://www.break.com (frame loads, and says "buffering.." forever)

http://video.yahoo.com (just get black window)

this applies to version 0.8.3 of the mozilla-gnash-plugin on firefox 3.0.3.  all of these sites do work just fine with adobe's flash 10 plugin on firefox 3.0.3.

in order to convince average users that gnash is indeed capable of meeting all/most of their needs, these less-common sites will need to be made to work as flawlessly as youtube.  i understand that it will take a lot of hard work to get there, but hopefully this list of problems is a good starting point.

thanks for all the hard work!