Sorry....Not alot of people this end of the pool at the moment.... my attention (as well as many others I'm sure ) has been elsewhere or I would have thrown some ideas your way...there is a flash workaround which may be of help with using pages and sites ..... You could use mythtv....you could try streaming from your laptop/desktop...feeds and podcasting is one thing I enjoy....for the most part I transcode alot of film and shows I wish to watch.... ...there is a list either in n800, n810 or in the OS2008 forum...(can't remem. which) that mentions some websites that stream film and live stuff well.....It is a no-thought/work option if you don't want to have to mess with transcoding or the hassle of finding and enabling feeds and casts......the lists may possibly have old or outdated links by now...but it most definitely would be worth checking out....Unless you beat me to it....Over the next couple of days I'll dig around for those particular posts see what I can find.
As far as firefox goes...there is the possibility of workarounds...hacks...updating the browser isn't going to happen....there simply isn't enough people who use the n800 for the firefox team to warrant the time and funds....fooling the browser or using a diff browser or application....ORB...or ..worldtv99 perhaps...with kmplayer is an alternative...there is also the possibility of utilizing turbo easy debian and running say...iceweasel or a program through it that would allow you to use youtube as well as many other programs for that matter.

Update:
http://talk.maemo.org/showthread.php...ight=streaming post 4 by Addison concerns downloading/transcoding method of youtube vids easy-peasy

http://talk.maemo.org/showthread.php?t=12496
2007 post but I believe sites like wwitv , favchannels.com still function fine
and there are many similar.....just a few suggestions ...
as far as current streaming media...lately....haven't played around with much shy of streaming from my laptop...vid and audio podcasts of shows and news...streamtuner and fm radio...
explore and I'm sure you'll find some cool stuff.