Well, there are literally thousands...possibly hundreds of thousands of applications for microcontrollers. Do you know what kind of microcontroller that you want to use? Or what type of application that you want to use the microcontroller for?
Or you can go to the microchip website and look under the application notes for a specific type of microcontroller, and see if that offers some good starting points. www.microchip.com
Otherwise, try google.com and search for "PIC schematics" or "Microcontroller schematics". The list is bound to have something that you can use.