There are 16 illustrations of free vector outline icons for web and mobile in this pack. The license allows you to use them in your commercial client projects as well, see the download file for details. The illustrations can be colored any way you choose, as it is all vector in the EPS 10 format!
You can automate the process of creation of such icons with some actions in Adobe Illustrator. How it can be done you will find out in new tutorials on the pages Vectorboom.