There are several tools that allow you to present images using a computer & digital projector. These tools are particularly useful for classroom presentations.
PowerPoint : Part of Microsoft's Office suite of programs. Add pictures to text presentations, or leave the text out all together!
Keynote : for Mac only. Keynote enables "cinema quality presentations for everyone"
Amazon Prime Photo : Amazon Prime Photos offers free online photo storage to Prime members, who can save and share unlimited photos on desktop, mobile, and tablet.
iPhoto (for Mac only, part of the iLife suite) : Apple's image storage software. Organize and edit digital images, then export to other applications in the iLife suite to share via e-mail, in print, and the web. Also offers a slideshow feature.
Adobe Bridge : part of Adobe's Creative Suite, Bridge indexes documents you produce using the various Adobe products, and provides easy access to Adobe Stock Photos.
The Snapshot tool in Adobe Reader allows you to easily select images in a PDF document, copy these to the clipboard, and save to another document or software program (Photoshop, etc.).
Follow directions on eHow.com or watch the video below (both are unaffiliated with Cornell University Library).