Animoto is a wonderful online movie maker that does all the hard work for you. Simply upload pictures, select or upload music, maybe add some words of explanation, and Animoto will do the rest; It'll automatically match the pictures to the music and creates a theme.
The free account only allows for a maximum 30 second slideshow, but there is an educational account that allows slideshows to be any length of time. The slideshow below shows off our 4th grade field trip to the Association For Craft Producers for our study in economics and business.
Animoto makes it easy to upload photos and present them. Here are some other field trip presentations for the lower grades that I put together that were used in our field trip celebrations: