I used all of the following to deliver video on the web since 1996 and set out a guide to help in your quest to find the best format to deliver your video via the internet.

Flash
As seen on YouTube, currently the most popular format with the widest computer support, but useless for mobile devices. Video was introduced with version 6 and has improved a lot over the past five years. Made by Adobe, formerly Macromedia. Free player.

QuickTime
As used for Hollywood movie trailers. Historically poor Windows support has improved with the popularity of iTunes (which includes the basic free QuickTime player). Made by Apple.

Real Media
Once a popular option due to excellent compression and cross-platform capability, now apparently in decline, though it is supported on some mobile devices. Made by Real, free player available.

Windows Media
An obvious choice on Windows, but not recommended for web use due to cross-platform and codec issues. Made by Microsoft, no longer available on Macs (though Safari can use the free Flip4Mac plugin).

ShockWave
Not strictly a video player, but video can be embedded in ShockWave files. Free player made by Adobe, formerly Macromedia, now effectively obsolete on the web (you should have been there in 1999).

Ogg Theora
Open source cross-platform alternative, not yet fully developed, patchy performance. May well suffer the same fate as Ogg Vorbis but popular with Linux users. Made by the Xiph.Org Foundation, playable in QuickTime, RealPlayer and some others using free codec.

MP4 and variants
Possibly the dominant format of the future - an ISO specification supported on computers, many phones, Nintendos and iPods (including the iPod Touch). Enthusiasm from Microsoft seems lacking but if you want one format that can be played on multiple devices this is currently it.

MIME-Types
Depending on the video format you choose and your server setup, you may need to set the appropriate MIME-Type using .htaccess - Mp4, 3gp and WMV all need explicit settings on the shared servers I use.

Embedding and EOLAS
In 2006 Microsoft changed the way Internet Explorer handles embedded content due to a patent dispute with EOLAS Technologies. This meant that the old methods for delivering rich media that were found in textbooks and software packages were no longer suitable.

The workaround is to use JavaScript to embed your videos in webpages. There are ready-made solutions available from the player manufacturers and others but essentially they all do the same thing.

I know that the patent dispute was recently settled, but I have no idea what the effect will be and as the JavaScript workaround conveniently provides valid HTML markup I don’t really care.

Streaming Video
It is technically fairly simple to broadcast live if you have a camera, and there is software available that will let you run your own TV station, mixing live camera and pre-recorded video.

You will need a streaming media server and some knowledge of firewalls and ports to do it, and a lot of bandwidth for each viewer, but embedding the stream in your website is no problem at all.