FlowDesigner is a free (GPL/LGPL) data-flow oriented development environment. FlowDesigner can be used to build complex applications by combining small, reusable building blocks. In some ways, it is similar to both Simulink and LabView, but is hardly a clone of either. FlowDesigner features a RAD GUI with a visual debugger. Although FlowDesigner can be used as a rapid prototyping tool, it can still be used for building real-time applications such as audio effects processing. Since FlowDesigner is not really an interpreted language, it can be quite fast. It is written in C++ and features a plugin mechanism that allows plugins/toolboxes to be easiliy added. FlowDesigner currently includes the following toolboxes: signal processing, audio processing (DSP), vector quantization, neural network, fuzzy logic, real-time audio effect processing (pre-alpha), linear algebra using LAPACK (pre-alpha), octave plug-in (pre-alpha) and robotics.