This video from TeacherTube is a great example of using web 2.0 services in a middle school science project. In this project students chronicled the process of photosynthesis.
Applications for Education
While this particular video is about a middle school science project the same methodology could be employed in a number of content areas and grade levels. In various fields of science students could use Blogger (or any blogging program) to chronicle the stages of a project including the initial hypothesis, testing of variables, failures and successes, and finally the conclusion of the project.
Another great use of blogging in English or Social Studies courses is to have students follow the developments of a news story and blog about their findings and reactions.