Bruce Land is showing off the hard work of his students in his Cornell University ECE 4760 Designing with Microcontrollers class. I hope you have a long lunch hour since it will take you a long time to go through all 35 projects. I found this Mechanix Motorized Guitar Tuner real interesting. Nice thing about all of these projects is the great documentation.

See the full list of projects 

"The Mechanix is a motorized guitar tuner for a standard 6-string electric or acoustic fixed bridge guitar. Named in honor of Megadeth guitar legend Dave Mustaine, the Mechanix is a unique and innovative product which has numerous patent possibilities. Our project may not be the coolest or most unique, but it is certainly the most metal. Traditional handheld guitar tuners are passive; they tell the user whether the guitar string is in tune, sharp, or flat, but the actual adjustment of the tension in the string has to be done by the user. This requires a fair amount of dexterity from the user, particularly when fine tuning is required. Thus, to increase both the convenience and the precision of the tuning process, we designed an active, motorized guitar tuner. The Mechanix responds to the user plucking one of the strings by turning the tuning knob until the string has reached its Standard Tuning note."