Zillow, the leading real estate and rental marketplace in the USA, uses R to estimate housing values. Zillow's signature product is the Zestimate, their estimated market value for individual homes, and it's calculated using R in a parallel batch job for 100 million homes nationwide. The process is described in this Slideshare presentation Data Science At Zillow by Nicholas McClure, senior data scientist at Zillow.
The Zestimate is generated through a series of processes built using various tools, including heavy doses of R, Python, Pandas, Scikit Learn, and GraphLab Create, the graph analytics software developed by Seattle-based Dato (formerly GraphLab).
The company makes extensive use of R, including the development of a proprietary software package called ZPL that functions similar to MapReduce on Hadoop, but runs on a relational database. The company is increasing its use of Python, which Zillow data scientists say is better than R for some things, such as conducting GIS analysis.
You can find more details on Zillow's data science systems at the link below.