From the OMB Blog:
Today, Federal CIO Vivek Kundra announced that the number of datasets on Data.gov has increased from 47 to more than 100,000 – with new sets being added continuously.
Data.gov was created to open up the workings of government by allowing the public to easily access datasets generated by the Federal government to perform research, build applications, and conduct analyses. Since its launch in June, Data.gov has received more than 18 million hits.