Are you interested in FPGA development but don't know where to start? Why not give Papilio a try?
The Papilio One is an open-source development platform based on the capable Xilinx Spartan 3E FPGA.
While FPGA devices are massively powerful and configurable, they haven't always been the easiest to develop.
Papilio attempts to remedy this situation by following the lead of popular microprocessor development tools like Arduino.
The Papilio One can be expanded by the use of "wings" which are stackable add-on modules, similar to Arduino shields.

You can still use traditional FPGA development tools to write code for the device. The Papilio isn't directly supported in Xilinx ISE but a script file is available on their website to load bitstreams generated by the program.

One unique feature of Papilio is that they provide a custom version of the Arduino IDE which allows to you write Arduino code and upload it to an AVR8 Soft Processor, an Arduino-compatible processor being emulated inside the FPGA!

Features:

• Fully Assembled with a Xilinx XC3S500E and 4Mbit SPI Flash Memory
• Provides an Easy Introduction to FPGA, Digital Electronics, and System on a Chip design
• Easily add New Functionality with Wings that Snap onto the Board
• Two-Channel USB Connection for JTAG and Serial Communications
• Four Independent Power Rails at 5V, 3.3V, 2.5V, and 1.2V
• Power Supplied by a Power Connector or USB
• Input Voltage (recommended): 6.5-15V
• 48 I/O lines!

Documents:

• Papilio Site
• Papilio-Arduino IDE
• Papilio Download Page
• Datasheet (Spartan 3E)
• Xilinx Download Page
• OpenCores Site