Are there alternatives to Beamer for slides ?

Under the topic Presentation Slides at The TeX Catalogue Online you will find some of them, beamer included.

Another list is provided at Screen Presentations Tools where Michael Wiedmann compares several tools and not only pdf oriented.

But, probably, the most updated list can be found at CTAN (Comprehensive TEX Archive Network) under topic Presentation.

There is also Lecturer which makes a pretty clean impression on me. Problem might be that it relies on genuine PDF features for the transition effects and overlays and thus needs a really compliant PDF viewer, which might mean that only Adobe Reader will do a good job. Notably, Preview.app won’t work in many cases. Still, if you only use the basic transitions, it may be fine with many viewers.

If you use KOMA-Script for anything else beside presentations, have a look at this short article in the PracTeX-Journal: http://tug.org/pracjourn/2010-2/hofert.html

»Abstract: In this article, we show how scientific presentations can be created based on the KOMA-Script document class scrartcl. The main advantage of the suggested approach is that the presentation slides allow for easy copy-and-paste of content from other LaTeX documents such as research papers or handouts. Using this approach, presentation slides are quickly generated, without the author having to learn how to use other LaTeX presentation packages. Additionally, in contrast to the rather overused templates of the more common presentation packages, the slides can be individually created and thus tailored to the topic of the presentation.«