Testimonial rotation that doesn't create pages for the testimonials. 150 Character max per testimonial.
An absurdly simple contact form plugin. Just type [contact]. There are no options.
Artiss URL Shortener will shorten a supplied URL using one of over 80 different shortening services
Threader is a very simple guestbook/forum/bulletin board system.
Dynamic Headers does just what you think it would based on the name - it allows you to create highly dynamic header space on your WordPress site.