[Calameo have changed things - post updated June 2013]
You can insert Calameo docs, by using an appropriate shortcode (for more on this, see my post on inserting Flash).
Note well: Calameo provide their own “WordPress” shortcode, but that shortcode doesn’t work on wordpress.com.
Visit Calameo.com, select doc, click Share, and copy the HTML embed code.
Replace this part:
with this shortcode:
Replace NUMBER with the actual number you can see after “books” in the URL of the publication (make sure you don’t insert any spaces by mistake).
Paste the end result into the “Text” post or page editor. The width and height numbers are just a suggestion: you can change them.
If you don’t want the links that will show above and below the viewer, you can paste only the shortcode.
Example (dimensions 550×400):