It's hard to find an online real estate site today that does not in some way incorporate maps. And so it's no surprise that another of the top ten tags at ProgrammableWeb is "realestate", now with 78 mashups tagged realestate.
A little over a year ago, Google released a new product called Google Fusion Tables. Fusion Tables allows you to upload, merge, share, and visualize large tables of tabular data. Basically, we wanted to answer the question “I have a spreadsheet. I want to share it with people and create a map/bar chart/storyline/other visualization.” Google Spreadsheets, while powerful, couldn’t handle the 100 meg upload we allow for Fusion Tables. And, being Google, we also provided something for developers.