Bulk Edit
You can perform bulk editing on any list views. Simply select
the items you will like to change by tick box clicking on the tick
box in the 1st colum on any list view. Then select actions drop
down and select bulk editing.

After clicking bulk editing option you should see the following screen. The contents of bulk edit will reflect fields available for the list you are on and will show you different fields for projects list to contacts list.
Here is an example of project list in bulk edit mode:

Here you can do various changes at once to selected projects. Change Client, Start Date, End Date, Project Status, Add Tags. Remove Tags