Wireframes

Often worked up from sketches to formal documentation, wireframes show the layout of an interface screen. Describes each element and behaviour. The focus is on layout, labels, and interactions. Avoids finished design elements such as color and photos, instead using placeholders for images, and sometimes copy.

They are used to communicate the specifications for individual pages or templates. Also used as prototype for usability testing. Prevents premature conversations about surface issues like color, instead focuses discussion on correct and complete content and functionality.

Wireframe sketches and final documentation are quite often kept confidential and aren't made available to the public. But the Wireframe Showcase site offers a rare glimpse at the UX work underneath the surface of the site.

via Wireframe Showcase

and OneXtraPixel

and Flickr Group - UX Sketches