http://www.mvps.org/skp/
Shyam Pillai, also a PowerPoint MVP, runs OfficeTips. This site offers VBA tutorials and samples, as well as both free and commercial add-ins. The add-ins and tutorials on Shyam's site include:
Handout Wizard
Sequential Save
Image Importer
Unflip
Save the Trees
Live Web
NoEsc
FaceID Browser
and many, many more
http://www.tushar-mehta.com
Tushar Mehta, an Excel MVP, has a site full of Office tips, tutorials and add-ins. The three PowerPoint add-ins Tushar lists on his site are:
PPT-Timer
Textbox from file
RandomSlideShow
For details on these tools, go to Tushar's site and click on the PowerPoint link in the left hand column.
http://www.aladat.com
http://www.soniacoleman.com/Tutorials/PowerPoint/acdpc_instructions.htm
AlaDat provides PowerPoint tools. The most popular of their tools are the CD creation tools and PrezGuardPro. In addition, they also sell SlideConverter. For details on AlaDat's tools, go to Steve Hetrick's site or Sonia Coleman's site