In a project report, there is a section called Project Users. There is a filter there for Home Team ID or Home Group ID. This will show you all projects that your team/group has touched. Some thing to keep in mind though: It works a lot like the People are in the Staffing area of a project. Sometimes people are put on the list because they were tagged in a status update or asked to approve a document. So you might see projects that appear on the list that your people are not actually assigned to a task.
If you see this, you can alway ask the project owner (or do it yourself if you have the access) to remove the person from your team on the project if they aren't assigned anything but might have been tagged in something. In the project, they go More tab -> Staffing -> People -> Select User -> Remove.
