Whether it's keeping track of your computer's memory usage or displaying information about the weather, dashboards are a fun way to track information. Adafruit shows off a way to build one using a Raspberry Pi that can track all kinds of data.
The guide walks you through setting up a variety of different displays, including both LED displays as well as a stepper gauge. Adafruit's version here uses either a dry erase board or a chalkboard so you can easily change the type of data you track without overhauling the whole thing.
It also shows you how to implement a number of different sensors, but it's certainly not limited by what they show you how to do. Once you have the basic concept down, you can really track and display just about anything you can imagine. Either way, head over to Adafruit for the guide.
Raspberry Pi Physical Dashboard [Adafruit]