I recently got a used Raspberry Pi and I've been looking at sensors and accessories available for it. Just to start poking around, I've picked up a temperature and humidity sensor, some LEDs, jumper cables, and resistors to play around with.

I got Arch Linux set up on the Pi serving a page, and I've gotten a script running hourly to get readings and populate the page with the last x set of readings. With the page I'm using Chart.js to render a plot.