Interestingly MS-Excel has an export method that can save charts into graphics file-formats. I couldn't see an equivalent while flipping through the PowerPoint object model, but I did come across this code snippet:

Private Sub App_PresentationSave(ByVal Pres As Presentation)
    With Pres.PublishObjects(1)
        PresName = .SlideShowName
        .SourceType = ppPublishAll
        .FileName = "C:\HTMLPres\mallard.htm"
        .HTMLVersion = ppHTMLVersion4
        MsgBox ("Saving presentation " & "'" _
            & PresName & "'" & " in PowerPoint" _
            & Chr(10) & Chr(13) _
            & " format and HTML version 4.0 format")
        .Publish
    End With
End Sub
[download]

This should save a file as both PowerPoint and HTML formats. You could implement this stub in Win32::OLE, if you can put up with the (very) low quality HTML MS-Office emits

But why bother? You can simply open the PPT up in PowerPoint, and save it as HTML.

Well, one good reason might be that the files are on a machine that doesn't have PowerPoint installed, such as a Unix-based web server that's trying to provide preview thumbnails for files that have been uploaded. (That's why I went looking...)

Assuming you have access to powerpoint you can also use the File->Save as...-> and then select file type gif, jpg or png and then you can save all slides as gif, jpg or png files. Depending on powerpoint version, I may need to modify your presentation slide sizes so that you get the appropriate image size.