Prezi has lately been getting a lot of use at various conferences. Initially Prezi presentations got a lot of positive reception just for the novelty, but I think it's used enough these days that that part might be diminishing. http://prezi.com/
OO Impress and Google Docs presentations are fine for relatively simple things. OO Impress can probably do more complex things too, but I find it sort of clunky to use.
I actually did one presentation in just some hand-coded HTML with prev/next buttons. One advantage to that approach is that you can fairly easily include editable, executable .js code examples.
But, don't expect the site to be completely without quirks. Leave yourself plenty of time to put the slides together, and export a file before your presentation just in case. I did have a little trouble getting their software to work occasionally.
Obviously you iterate over the process. If you do it in powerpoint or keynote, it sucks. Are you manually going to copy paste the code every time?
Use latex with beamer class. Even tho' it is old, when customized, it _is_ still the best way to do presentations.
<shameless plug>
I created a (what I believe is) awesome presntation: http://www.slideshare.net/scorpion032/building-pluggable-web...
using Beamer class and here are the custom commands used: http://github.com/becomingGuru/gids-django-ppt/blob/master/c...
</shameless plug>
But if you have a complex presentation, or you're a stickler for detail, I recommend creating each of your slides in Inkscape or Adobe Illustrator, and stitching them together with something else. It's the only way to get the design just right.
Perhaps I'm over thinking this and should just use Google docs.
When I used Linux, I just used the Google Documents presentation maker.