Resource types

I believe another option is to import your powerpoint into a lesson module which is an integral part of moodle. You have to save your ppt as html and then zip and import to a lesson. Note - you lose some functionality - such as the animations and perhaps some graphics. On the flip side - you can add questions, grades and other things available in lesson module.

See detailed instructions here: http://docs.moodle.org/en/Import_PowerPoint