Below is a visualization tool we use in our research. It is written in java, and consists of one class called QCircuitDisplay (source). The circuit you see is the result of a run of the optimizer on the cybenko decomposition of a randomly generated 8x8 unitary matrix. The definition of R, S, and T gates can be found here, and for an explanation of the notation used in drawing the circuit, consult any introduction to Quantum Computing, such as this paper by Dorit Aharonov
To scroll, use the buttons on the sides.