The Tasks Report lists all tasks in the current space, and allows you to filter by assignee, and task status.
By default, this report is only available to users who can Add content (pages or blog posts) to the space.
Admins can make it available to everyone by changing the Workflow Activity and Drafts Visibility setting.
Viewing the report
Choose Space Tools → Tasks to view the Tasks Report:
Here's what the report looks like: