We have been building a piece of software that allows you to log data from the arduino straight into excel. It also allows you to turn the digital pins on. Its great for testing things out. We are adding SPI, and I2C to it as well. The arduino acts like a pass through device and allows you to communicate with sensors and other boards really fast.
Its $5.00 and this cash is being used to add more functionality to the program.
Feel free to share thoughts and ideas for future revisions.
Thanks for looking!