This is worth a heartfelt OMG: Nancy Duarte’s Resonate is now available as a free download from iBooks. You need an iPad or a Mac to use this version, but it has all sorts of interactive goodness and bonus material, including lots of video.
I’ve gone on about Resonate at length before, but to recap: if you write or deliver speeches and presentations, it’s absolutely invaluable. (And if you don’t have an iPad or Mac, you can always buy it minus the supplementary content.)
Go get it!