What what I can read there isn't an easy way to do this without costing money.
Powerpoint has a export feature to save it as HTML files but of course you lose everything that powerpoint does, such as animations, transitions etc. So if all you want to display is your powerpoint content online then that will be the easiest way to go about it.
If you want to keep your animations, transitions etc, then it'll need to be converted to Flash which I guess takes some work to get it in there, unless you pay for some special tools.
I haven't done it myself so I don't know how hard it will be but here is a little tutorial to manually
convert ppt to flash. I also see this company sells software to do this automatically but it isn't cheap.
Good luck