If you like playing with audio the ElmGen DSP Development Tool will help you with that.  It uses an Arduino to control a Spin Semiconductors development platform directly. When the dev tool is hacked it opens up lots of opportunity to make it perform in more powerful ways.

“Key Features:

• Cross-platform development tool for Spin FV-1 effects processor
• Testing and production EEPROM programming capabiltiy
• Built-in real-time hardware simulator of FV-1 DSP core – hear and test your algorithms digitally
• Written in pure Java (requires RXTX for EEPROM programming)
• Works on Windows, OS X and Linux (Linux not tested)
• Advanced coefficent calculations or code manipulation possible with Java – e.g. conditional compilation, high-level code blocks, etc. not possible with SpinASM
• Completely free and open source (GPL) – Users are asked to contribute their changes back to the project for everyone’s benefit
• Code generated can be used in commercial closed-source projects
• Licensed as GPL3 – see: http://www.gnu.org/licenses/“