ZPUino is a project that offers a microprocessor that can be put on FPGA, and that can be programmed with a simple IDE. Everything is open source: the toolchain, the IDE and the VHDL code; and it can be downloaded freely.
The hardware architecture is based on the ZPU (Zylin CPU), which is a processor designed to be simple, small and easily placeable inside an FPGA (which is why is called a “soft” processor). The HDL source code of the ZPU can be freely dowloaded from Zylin’s web site.
The graphical development environment is a modification of the Arduino IDE. The software is compiled using a custom GCC toolchain that includes the necessary libraries to access the hardware peripherals of the ZPUino.
The FPGA where it has been developed is the Spartan3E.
The project is still in its Alpha stage, but I am keeping an eye on its evolution from now on. Someday it could become a real microcontroller chip (no FPGA, directly on silicon), it will be completely open source down to the register level (RTL) and it will have performance potentially higher than current Arduino, because it’s 32bit and it already reaches 100MHz on FPGA.