WebMaestro.Fr

Upload the layers of your image, and create a parallax effect !
It works great on smart devices too !
The first step is to create with your favorite picture editing software (Photoshop, GIMP…) an independent image for each ground composing your image. All these layers shall be the same size, and should be in .png format as they are meant to include transparency areas. 
Then, on your post editing page in WordPress, click the Insert Media button, and (the same way you would create a gallery) upload your layers under the Create Parallax item. Reorganise the layers if needed, from the background to the front. 
You can finally configure the animation (calibrate, invert, limit, scalar, friction), and publish !
There is <a href="http://webmaestro.fr/image-parallax-plugin-wordpress/" rel="nofollow ugc">some examples</a> on the plugin page.
It uses <a href="http://wagerfield.github.io/parallax/" rel="nofollow ugc">parallax.js</a> by Matthew Wagerfield.

Image Parallax

Create images with a parallax effect. Upload some layers, configure the animation, and publish !

wp-maverick

MBA Multimedia

This plugin aims to help WordPress users or developers to add – very easily – several UI elements to their websites, including 3D components and layouts based upon the work of the <a href="http://w3d.mba-multimedia.com/" rel="nofollow ugc">W3D project</a>.
Thanks to dedicated admin settings screens and a powerful shortcode system, creating, customizing and adding complex elements to a WordPress website is really fast and intuitive. The plugin offers a wide range of components from sliders to HTML layouts.
The plugin will help people to customize their WordPress site even if they don’t know HTML, CSS or PHP. Developpers who know these languages will be able to customize the plugin by adding their own stylesheets or templates. Various WP filters are also available to help wordpress developers customizing HTML output.
See the <a href="http://wordpress.mba-multimedia.com/en/our-plugins/wp-w3d-plugin/" rel="nofollow ugc">official plugin page</a> for more informations and demos (EN/FR).
This plugin is based upon the work of the <a href="http://w3d.mba-multimedia.com/" rel="nofollow ugc">W3D Project</a>‘s consortium and created by the french Web agency <a href="http://www.mba-multimedia.com/" rel="nofollow ugc">MBA Multimedia</a>

WP W3D plugin

WP W3D aims to help WP users or developers to add easily several UI elements to their website, including 3D components and complex animated layouts.

Image Parallax vs WP W3D plugin