Workshop- Have students provide peer review for each other's assignments directly through Moodle. You're in charge of setting the timeline for several stages (initial submission of the work, peer review) and how many assignments each student reads.
Quiz- You can build a bank of quiz questions and use them in a various quizzes.
Lightbox Gallery- You can use this module to create an image gallery. Great for displaying images of ideas generated together on the board in class.
Scheduler - Set aside time slots so students from a single class can sign up to meet you.
Glossary- The class can work collaboratively to create a glossary of terms, with each student adding entries.
For the motherlode of information, visit Moodle.org, the official Moodle help & how to site.