Fusion Tables is an experimental data visualization web application to gather, visualize, and share larger data tables. The Guardian newspaper makes active use of this as part of their pioneering data journalism work.
You can easily upload data sets from CSV, KML and spreadsheets, and visualize the data using a variety of tools. Users can merge data from multiple tables and easily visualize large data sets on Google Maps.
All you need is a Google Drive account to get started.
How to create thematic polygon data maps is an excellent step-by-step guide to walk you through the process of making your own maps.
KML boundary files for Bradford