Stacks is fluid layout for RapidWeaver. Stacks is designed to combine the drag-and-drop simplicity of Blocks with the power of fluid layout. Stacks lets you build pages that flow text to the dimensions of a theme even if the theme has a variable width. You can build flowing columns, flexible rows, and tiles of images. You can build columns within columns within rows within columns. Or group a stack of objects inside a box. Almost anything is possible with Stacks.
Licence : 19$95
http://www.yourhead.com/stacks/index.html