Tefltecher has a post on an online app called present.me with which you/your students can record themselves giving a powerpoint presentation by webcam (something students have at home, cough). You need to sign up but it's free.
Tutorial and a lesson plan on public speaking using present.me at Ian´s pucker Tefltecher blog, inc. a how not to use powerpoint vid here
More on public speaking:
Kieran's The King's Speech lesson at his splendid film english site.
Some adaptable stuff at eHow
A powerpoint on powerpoint:
(or how present.me can help)
