About two months ago, I shut down the old Project Weekend site for good. Since then I worked on a major revision to my home server project: Holly. I wanted to move it off of my local network and give it a home on the web. With an extra domain sitting around, it only made sense to use it: http://holly.projectweekend.net.
Holly receives data from a sensor board connected to an Arduino Mini Pro 3.3v running: https://github.com/projectweekend/Ar-Starbug. This sketch handles receiving commands via the serial port, reading the requested sensors, and sending the result back through serial.
Connected to the Arduino is a Raspberry Pi running: https://github.com/projectweekend/Pi-Red-Dwarf. A cron job fires off every 15 minutes asking for a sensor reading through the serial port. Once it has the data it makes a web request and sends it to Holly for storage in the database.
Why did I organize things this way by using both a Raspberry Pi and an Arduino? Well, there were already stable Arduino libraries for each of the I2C sensors I was using. The Raspberry Pi can do I2C, but there is just not as many supporting libraries. Additionally, grouping the sensors with the Arduino made that piece more modular. Those parts can now be dropped into any other project with a serial port.
The final reason has to do with making web requests. That's how data gets transmitted to Holly. It's really easy to do in Python plus the Raspberry Pi has a built in way for scheduling tasks to run on regular intervals thanks to cron.