We have to prepare video training programs for various modules.
Please contribute with your valuable suggestion regarding the video file format which lead to the smallest file size and tools used for it.
It sounds like you might want to search for and contact various vendors with your specs. Things to consider:
1) video files are not small by nature
2) depending on the duration - small may make it difficult for your audience to see any details you do not want overlooked.
3) do you have formal specs that indicate what platforms and resolutions you want to support?
WMV (Windows Media), RM (Real Media) and RMVB (Real Media) are among the smallest. Ofcourse as J points out it depends on the resolution. If you want you can buy commercially available video editors that will encode higher resolution vids to lesser resolution ones in smaller files.
(I'm hiring Software Development Engineers in Test in Seattle, WA)
as JP points out, there are many other factors besides the smallest. Also consider what your average user will have installed on their machine. If you choose something like Realmedia or Quicktime, they'll have to install a plugin to use it and the slightly smaller size may not be worth the support calls you get.