If you need to create a schema for your next DIY project maybe Fritzing is the right tool.

Fritzing is a visual editor of circuits. In the editor you can find all the necessary components like resistors, LEDs or sensors to put in your breadboard. The editor offers also well know boards series like the Arduino one.

Are you looking for a particular parts not present in Frizting standard distribution? No problem, here a link to a community list of user-made components: http://code.google.com/p/fritzing/issues/detail?id=875