Fancy Before After Compare Image Module is a nice Joomla addon, where you can show the before and after effects by defining two images. Compatible with all the Joomla versions and best used by doctors, architects, designers, etc.
You can see the demo on the left top of the page here.
Vertical Sliding panel is a nice sliding panel on the top template side position. You can define the contents within the sliding panel. Highly configurable and backed with a 24x7 Customer Support package. This module is cross browser compatible and works on all the modern browsers. Bug Free and works great! Compatible with Joomla 1.5.x , 2.5.x , 3.x.x. The Downloads Access and Extension Support is valid for 6 months from the date of purchase.
Module Parameter Screenshot