Microsoft Office online offers free access to their repository with more than 1000 free templates that you can download for your presentations. All these templates provided by Microsoft can be used to create presentations with PowerPoint.
The site is organized by application and then by topic. You can download free templates like the education collection that includes tools for teachers or surveys for students. There are also addins like Mathematics addin or Chemistry addin for Microsoft Office.
For example you can download this free powerpoint presentation, a professionally-designed template has a dynamic timeline in a SmartArt graphic. Complete instructions for reproducing this slide are included in the Notes pane with template with animated arrow created using SmartArt objects. Complete instructions for reproducing this slide are included in the Notes pane.
Download it from here.
Find more information in Microsoft Office online