I always find it helpful to watch instruction in action as I am trying to understand how the process works. The Teaching Channel has 16 videos on its site which are tagged as PBL. They cover a variety of topics.
What is It? Project-based learning is an instructional strategy in which students work cooperatively over time to create a product, presentation, or performance. The two essential components of project-based learning are an engaging and motivating question and a product that meaningfully addresses that question.