Digital Vector Maps provides several hundred maps on their site. Most maps are available in Adobe Illustrator and PDF format; so, you’ll need to resave them in a PowerPoint compatible format if you want to use them in your next presentation.
Shelly from Digital Vector Maps informed me that all of their blank outline state maps for the US are available at no charge. For example, here’s a link to the page for the California state map.
Other maps need to be purchased, and most maps range from $3.95 to $279.
The royalty-free maps are fully editable in Adobe Illustrator 8 or higher, with all major map features residing on intuitively labeled layers to make possible separate editing of such map elements as lines, colors, symbols and text. Such objects as geographic place names, country borders and reference text are provided as separate editable objects.