There's a good article over at Linux Revolution about the gaping hole in the Free Software desktop - the lack of a good presentation application.
I also remember rumours of adapting AbiWord to do slideshows as well (look for AbiPresent).
I'd like to see Inkview get more backing. It comes from a strong SVG background with Inkscape, meaning it is designed around the graphics rather than designed as a Powerpoint clone. I think that's the kind of approach that is needed here, something a little "outside the box" compared to the standard.
Anyway, the article is a good read (as are most of the LR posts) with some good comments so head over and check it out. :-)