Masonry is a dynamic grid layout plugin for jQuery. Think of it as the flip-side of CSS floats. Whereas floating arranges elements horizontally then vertically, Masonry arranges elements vertically, positioning each element in the next open spot in the grid.
The result minimizes vertical gaps between elements of varying height, just like a mason fitting stones in a wall. This project lives on GitHub at github.com/desandro/masonry. There you can grab the latest code and follow development.