Is there a program that I can use as a
on Mac OS X (10.6.2) during presentations?
I don't have and don't want to use hardware one.
Additionally there is Mouseposé. Not free but does more than OmniDazzle. It also offers the ability to show your keystrokes on screen.
I know that you only asked about mouse pointer/highlighters for presentations, but another thing that is useful at the same time is keystroke highlighter or on screen display. In fact, I found your superuser post when I was looking for just the keystroke highlighter. :-)
Anyway, I eventually found something: KeyCaster
Combined with OmniDazzle and you have a full presentation kit for highlighting your mouse and keyboard actions.