A somewhat forced vacation, caused by a 50% increase in family size (sometimes, constants DO matter !). While I recover, look over this set of recommendations on giving scientific talks, by Robert Geroch.
Whenever I see suggestions on how to use powerpoint effectively, I see these inane comments like "never use more than 6 words per slide" and what-not. For high signal-to-noise ratio presentations like at conferences, this hardly makes sense. The suggestions given above are remarkably intelligent, and are directed towards scientific talks. The fact that this was written in 1973 only goes to show that the principles of good public speaking are timeless.