Here's the Google Code page and below is a video on it's data cleaning tools. Google Refine can also transform data and access external data (like JSON data) from other websites, but I've found it most useful for data cleaning.
Sunday, April 17, 2011
Data cleaning with Google Refine
There's a lot to be said about the data and text cleaning abilities of programs like R   and Stata   . But when it comes to cleaning up data with lots of spelling errors, different forms of the same string, abbreviations, acronyms, etc - or - if you've got to task a student worker who's skill set barely includes M$ Excel, then Google Refine (it used to be called Freebase gridworks) is a great tool for cleaning data.