Bulk creating activities really comes in handy when you have a lot of the same type of activity but with different customers.

You can do this in the Contacts view. there you can choose exactly which persons you want as participants.

Filter out the contacts you want to create an activity with and click Create Activity in the tab bar that appears when ticking a box. Choose Activity Type, a Description and voila! You have now created several activities of the same type with different contacts.

Head over to your list of Activities or your Calendar and you'll find the new activities there.