eVince can do pdfs, which I believe are the second most popular presentation format. You can use OOo on the desktop to export ppts as pdfs.
Well, there's dia, for drawing. I now use Xournal for the note-taking I used to use Mpad+ for. Doesn't do quite everything M+ did (notably the only "shape" available is a straight line, all else is text or free vector sketching, also no checklists, etc.), but does a lot more (highlighting, marking up pdf, exporting as pdf).

Best sol'n in general is rdesktop or vnc to a machine with OOo, if you need MSOffice compatibility. Of course, that requires network access.