Three sets of icons dcash, dschool and dosx from dellustration.com.

• dcash is a single icon file of a huge dollar sign
• dschool is a set of four icons consists with pencil, notebook and school black board
• dosx is a set of application icons in 3D view

I alway admire those make good icons, since I dont have that kind of talent I always collecting them and help the author promote their work.