You can mass update tags, source, stage, and people assigned to contacts using mass actions.
From All People, select the people you would like to change on the left hand side, then select the appropriate button at the top.
Batch Email - This icon allows you to send out an email to all selected people.
Reassign - This icon allows you reassign multiple leads at one time.
Add/Remove Tags - This icon allows you to add a new tag to multiple leads or remove a tag you do not want anymore
Trash - This icon allows you to trash the selected leads all at once. *Note - Trash is not the same as 'Delete'
Export - This icon allows you to batch export the selected leads out of Follow Up Boss.
To mass update an entire list at once, click the top select box then the select all link that appears.
Be careful when using select all on large lists and "All People" as there is no undo