A compact, rugged, and portable fluorimeter was designed and constructed using a 460 nm light-emitting diode for the excitation and a silicon photodiode for detection. The total cost of such an instrument is less than $110, thus allowing for deployment of multiple instruments at low cost. The fluorimeter is easy to operate and has been successfully used to quantify fluorescein in commercial-brand antifreeze and chlorophyll a pigment in spinach leaves. The mini instrument and the associated experiments have provided for a novel approach to teaching the principles and applications of spectroscopy and fluorescence to a wide academic variety of students. (Contains 4 tables and 2 figures.)