There are seem to be many class libraries that you can use to do a presentation in Latex. I have found the Beamer class. I like the PDF slides produced using the Beamer class. I have not yet tried other.
Beamer is a German word. It means a projector.
Example of slides using the Beamer class : http://www.informatik.uni-freiburg.de/~frank/ENG/latex-course/latex-course-3/latex-course-3_en.html
