PowerPoint Paloooza
This site is one of the most visited sites for US history teachers on the Internet. It is mostly visited for its wonderful PowerPoints that you can download and adapt to your own class as well as a ton of useful links. The New York based teacher also is continually updating the site.

Check out this SlideShare Presentation:

Antebelleum Southern Society

View SlideShare presentation or Upload your own.

Powerpoints
I have been working with an online US history book (found here) to help create an interactive textbook site and this is part of what we are thinking of adding to the site. If you go here, there are some rather good slideshows (one is above) and after you see one, other related ones appear so while the original site has just a few entries you end up with many more. You can also change your Power Points into narrated movies.

Powerpoints for the American Pageant
Here is a powerpoint for every chapter of the book and could easily be adapted for other textbooks.