The Teensy is a complete USB-based microcontroller development system, in a very small footprint, capable of implementing many types of projects.
There are a number of shields available for these microcontrollers, including the OctoWS2811 Adaptor which facilitates the control of thousands of LEDs and the Prop Shields which are aimed at building small hand held props. There are also audio shields which combined with the browser based audio design tool, provide a quick approach to low latency real-time audio processing.
Here are some links to get you started: