Ground School Presentation Materials

Hi All,

I am a fairly new CFI-G, just completed my second season teaching.
at a small but growing club. One area of opportunity we have for improvement is in preparing our students for the written and oral exams. To help with this I am thinking of running my first ground school.

I am looking for Ground School Presentation Materials. PowerPoint Slides and/or other electronic media I can use to produce PowerPoint presentations. I found some for Airplanes that could be purchased but not for Gliders.

This is a club environment, so Instructors and Tow Pilots don't get paid. I am willing to spend some money for materials, but free would be better as it will be coming out of my own pocket. Yes, I could pass on some of the cost to the students, but would prefer not too, if possible. In either case paid or free let me know what you recommend.

Thanks
Bill