There aren't any PowerPoint presentations available here online, but the documentation is quite comprehensive, and you should be able to build one yourself without too much trouble.
In order to get department head buy-in for our mojoPortal implementation project, I did create a PowerPoint presentation about two years ago, that talks about the benefits a CMS would bring to the City's web presence. It's text only, so I'll copy it below in case you find it useful in your own:
Current Web Site
- Outdated design
- Centralized editing—requires specialized knowledge and security
- Much of the site stored in PDFs—not as useable/searchable as inline text.
- Changing site look would require editing thousands of individual pages
Content Management System
- Modern web site design and structure
- End users can edit pages in an easy, familiar manner
- Audit trail and "undo" capability, with optional content approval
- Search, site map, and many other important features built in
- Overall site look can be easily changed
CMS Effect on Departments
- Ability to take ownership of your portion of the site—keep content fresh and relevant
- Make updates at any time—no need to wait for IS intervention
- Some initial training will be required
- Published URLs will need to be changed
- IS personnel will still be maintaining the site and providing any needed assistance
Live Demonstration... (this was done from a demo site)
CMS Benefits for the City
- Content and presentation kept separate
- Decentralized editing and publishing
- Consistent, easy to change site look and feel
- Instant publishing—e.g. City emergencies
- Integrate content into site instead of PDFs
- Integrated features (calendar, forms, blogs, forums, maps, polls, image galleries, RSS, site search, site map, Flickr/Twitter widgets)