The hammerhead, hairpin, HDV, VS and glmS ribozymes are the five known, naturally occurring catalytic RNAs classified as the "small ribozymes". They share common reaction chemistry in cleaving their own backbone by phosphodiester transfer, but are diverse in their secondary and tertiary structures, indicating that Nature has found at least five independent solutions to a common chemical task. Fluorescence resonance energy transfer (FRET) has been extensively used to detect conformational changes in these ribozymes and dissect their reaction pathways. Common and diverse features are beginning to emerge that, by extension, highlight general biophysical properties of non-protein coding RNAs.