This is not new, but I like it, and I thought I'd show it off.
So here's a slideshow of my public Flickr images.
You can grab the code by going to your photostream and clicking on the Slideshow link just under the search box. Once in your slideshow, click on on Share in the top right and grab the code. Easy-peasy.
Would you like to see this in a window by itself? Click on Slideshow in New Window then why don't you?