If you convert the powerpoint presentations to flash, that will reduce
file size by 90%.
Actually, the converted flash can be bured to CD too or upload to
Web.
That means, you can access to these files with internet connection.
You can only need a web browser to view these flash presentations.

To convert PowerPoint to flash, you have three options

Option1. Convert PowerPoint to flash manually
If you have some programming experience, you can do the conversion
manually.
See this tutorial:
http://www.sameshow.com/other/powerpoint-to-flash5.html

Option2. Convert PowerPoint to flash with a FREE converter
If you have a simple PPT file and do not care about the animations,
transitions, audio and other, you can use a FREE converter Powerbullet
Presenter.
It is a small, simple and free program for creating presentations in
the Flash format.
http://www.powerbullet.com/

Option3. Convert PowerPoint to flash with a commercial converter
For a complicated PPT file, you always should use a commercial
converter like
PPT2Flash Standard

How to use it from
http://www.ppt-to-dvd.com/forum/viewtopic.php?t=1514

Free Trial from
http://www.sameshow.com/download/ppt2flash-download.php?sid=5

Also, some tips to reduce the file size of a powerpiont presentation
http://www.sameshow.com/other/powerpoint-to-flash7.html