Video on websites, what format.

[#1]

I am including video files on my website here: www.seanbranagh.ie/media
I have already included the obvious Windows Media files. Thinking of those without Windows Media player, what should I include, Quicktime or Real Player files?
Don't want to waste disk space by including all of the different formats!

[#2]

Ogg Vorbis is platform independent.
Wikipedia uses it http://en.wikipedia.org/w/index.php?title=Special:Search&search=%20video&fulltext=Search&ns6=1&redir...

[#3]

The most ubiquitous format currently recognised is DivX in an AVI container format.  Pretty much every player on every platform should be able to handle it.
I would be tempted to have .AVI, and also a .MOV primarily for Mac users.  That should give you decent coverage of the entire market.
Whilst Ogg Vorbis is a good codec it does require a codec download, and for most Windows Media or Mac users this would be an additional step to be explained.
B.

[#4]

I would be tempted to use the format .flv, you can get a really good free converter from Riva at: http://rivavx.de/index.php?downloads0&L=3
You will then be able to get a player for your site at: http://flowplayer.org/ or just do a google search