I am an English teacher and my students must do a 5 minute demonstrative speech everyyear. I model the project to my students by performing a demonstartiver speech mysel before they do. My topic every year, pitching. It is my favorite day of the year because I get to combine my two passions, teaching and fishing. First I give a very brief history of pitching, then the equipment needed, and the motions of how to do it. I pitch a jig into a measuring cup and my students go nuts when I get it in from like 20 feet out. If you can pitch, might be worth a try. For visual aides, I bring in a DVD on pitching as well as pictures from magazines of pro doing it.
Good Luck
P.S. I also used to do public relations and I gave a lot of speeches, so if you have any questions about how to give the speech or need some tips just PM me.