<p>I have some code documentation in MS Powerpoint 2003 that I'm revision-controlling in an SVN repository. I'd like to auto-insert the latest revision number into this document whenever I open it. I am using TortoiseSVN. I've been able to google up a macro or two that might work but wanted advice from experts. :) Thanks!</p>

I think it should be possible to use the $Rev$ macro inside it with the Office 2007 XML formats, but I am not too sure what will happen with older formats that might contain binary data. You might need to tweak svn settings a bit so it sees .ppt files as text and not binary for this to work, I am not sure what is the default behavior. See svn:mime-type for this :
http://svnbook.red-bean.com/en/1.2/svn.advanced.props.html
Read this for detailed infos on $Rev$ replacement:
http://svnbook.red-bean.com/en/1.4/svn.advanced.props.special.keywords.html