What is a website where you can make a slideshow?

I can think of two types of slideshows. One where you view your favorite photos, and the other where you are giving a speech and want some visual aids.

You can easily create free slideshows with various free softwares. Irfanview is a relatively popular, well established example that is a low resource user. A more robust example might be google's free Picasa 3, which is a much more polished photo catalog, with the ability to do slick presentations of your photos.

For a visual aid type slideshow you might try docs.google.com or OpenOffice.org, (and there are many others available by searching such as "online presentation docs"