The beamer class is a LaTeX class for creating presentations. The class has been under development since 2003. The development is hosted at sourceforge.net/projects/latex-beamer.
PGF and TikZ are TeX graphic packages. PGf must be "programmed", which makes it quick. TikZ is build on top of PGF and allows you to create sophisticated graphics in a rather intuitive and easy manner. The development of the packages is hosted at sourceforge.net/projects/pgf.