As explained in part 1 of this series of posts, the gigya shortcode allows you to use flash objects in a wp.com blog.
“Flash objects” includes Flickr slideshows (but be careful with copyright issues).
If you have enabled auto-embedding in Settings>Media, then you should be able to insert a Flickr slideshow simply by pasting its URL (http…etc.etc…/show/ ) in the HTML post or page editor (thanks to Jennifer for pointing out). If this won’t work, you can use the workaround described here.
The URL model for a Flickr photo set is this:
To insert it as a slideshow, you need this shortcode model:
Paste into HTML post or page editor, or into a text widget. Where I’ve written SPECIFY, you type in the desired width number; make sure it doesn’t exceed the maximum for the theme you’re using (see relevant posts here and here).
(Night Shots – photos by Christopher Schoenbohm)