I was recently perusing a photographic forum where I generally like to visit periodically and they were recommending an application called "ProShow Gold" from photodex. I recently downloaded a trial version of this application to try it out and found it to be great. It is a very cool product that allows you to take multiple pictures and put them into a slide show with synchronized music. It offers an abundence of transition options and output formats. I player around with it briefly and created a short 4 minute show.
The results were stellar. It took only about an hour to produce, and the output looks very professional. The only issue I am facing now is how to post the output to the web. I am still struggling to find the best encoder to create the smallest size image and most widely compatible format. Regardless, I highly recommend this application.