http://www.daz3d.com/rons-cracks
Photoshop brushes of real genuine cracks of paint, rock, asphalt, wall, wood, and some hairline fractures. Plus one custom brush to make your own cracks!

There are also some layers styles to add a 3D look. Glass cracks are not included since a separate set is devoted to just that. Create interesting backgrounds, explore, have fun, and create.