Seeing how things change over time can be important for a business so that you can figure out what works best. Square, the company that turns your iPhone into a credit card reader, just released Cube, an open-source system to help you visualize time series data. It's built on MongoDB, Node, and D3.
Once you're all setup server-side, it's pretty quick to put together a dashboard, as shown in the video below:
A lot of the boiler plate time series work is done for you via the visualization components, but if you want to dig deeper, you can also access Cube's query and aggregation functions. This gets you sums, medians, minimums, maximums, and some others, as well as clumping by minutes, hours, days, weeks, or months. If you've done this sort of a stuff with your own code before, you know how annoying it can be.
Cube is still a work-in-progress, but with Mike Bostock, now a visualization scientist at Square, this could be something to keep an eye on.