Google Fusion Tables
What it does: Makes it easy to manage and visualize large datasets in the cloud.
Why it's cool: So many reasons! The initial gallery of datasets is phenomenal, including info on climate change, health statistics, and country flags, to name a few. Charts and maps can be exported to Web sites and will update automatically. You can collaborate on the data itself with Google's normal functionality, apply filters, merge data from multiple tables… plus it's just fun to play with.