So -- for my very first book trailer I tried some of the free software that came with my computers, Windows Movie Maker and Microsoft Photo Story for the PC and iMovie for the Mac, but they seemed a little limited. I didn't want to spend a whole lot of money for Adobe Premiere, so I settled on Pinnacle Studio Ultimate for $129 bucks and I'm very happy. For sound effects I joined "The Freesound Project" which is a really cool site (and made me go out to buy my own little Sony digital recorder so I can start recording my own effects.)
This was a really fun little project. A few hours yesterday doing a "first draft," then a few more hours today tweaking in all the great input I got from my friends.
Sound credits here: http://www.youtube.com/watch?v=h0N7XRBeyhI