Here a procedural leather material for cycles is. There is a brief explanation in blenderartist. This zip includes six leather colors and two kinds for each one: new or worn.
The model is made by @Tuqueque. You can download from blender demo files.
I hope you like it.
I have updated the file to Blender 2.69 version. Now the materials have less texture nodes so they should render faster. I have included a new preset for each color, cracked leather. So the new file includes 18 leather presets, which look better than the old ones. Also I have left the old 12 presets. Their names are ended by "_268".
I hope you enjoy them.