Once you start having a lot of playbooks and some reusable tasks, you might want to organize them::
playbooks/
tools/ # Used to manipulate some hosts. Ex: ping, show_groups
actions/ # For actions. Ex: update, sync, restart, ...
provisionning/ # Run once provisionning playbooks. Ex: configure ssh, install python, ...
hosts/ # For playbooks manipulating a single host
service/ # Content related to a service manipulation. Ex: deploy monitoring on all hosts
.. note: There are various ways to organize playbooks, this is a first draft at how they could be organized