I've gone through a few iterations of presentation packages for LaTeX. ppower4 and prosper were good alternatives at one point.
My current favourite is beamer.
Here are some sample talks written in beamer.
rpm-talk-2 tex pdf
card-pu_ias tex pdf
Giving technical talks requires a lot of verbatim in these slides, to compile cleanly you need [includesverbatim] in the options to any frame that contains verbatim.
I also use the alltt package more than verbatim, so I can change colours and add symbols as necessary.
