The much-anticipated US government catalog of government agency web sites who offer structured data, Data.gov, has gone live. It’s a first cut at what should grow into a very useful index of a vast array of government data that’s available online. Here’s how they describe their site and their mission:

The purpose of Data.gov is to increase public access to high value, machine readable datasets generated by the Executive Branch of the Federal Government. Although the initial launch of Data.gov provides a limited portion of the rich variety of Federal datasets presently available, we invite you to actively participate in shaping the future of Data.gov by suggesting additional datasets and site enhancements to provide seamless access and use of your Federal data. Visit today with us, but come back often. With your help, Data.gov will continue to grow and change in the weeks, months, and years ahead.

The current Data.gov catalog includes 47 data sets that can be accessed in XML, Text/CSV, KML/KMZ, Feeds, XLS, or ESRI Shapefile formats. See the FAQ for additional information.

Data.gov was released to the public as part of the Obama administration’s Transparency and Open Government Initiative. Although the preliminary release offers a limited subset of the government’s data, it’s a good first step and certainly an improvement over any earlier government-initiated efforts (or lack thereof) to make federal data accessible and downloadable.

Data.gov’s catalog is divided into two sections: a “raw” data catalog and “tools”. Here’s their description and a screenshot:

• A) “Raw” Data Catalog: Data.gov features a catalog with instant view/download of platform-independent, machine readable datasets in a variety of formats
• B) Tool Catalog: Data.gov features a tool catalog to provide the public with simple, application-driven access to Federal data with hyperlinks. This catalog features widgets and data-mining and extraction tools, applications, and other services.

As identified in the Data Policy page, the site is expected to evolve based on stakeholder participation:

In support of the Transparency and Open Government Initiative, recommendations from individuals, groups and organizations regarding the presentation of data, data types, and metadata will contribute to the evolution of Data.gov.

Time will tell how much input from third parties will shape Data.gov, but it’s nice to see that it has been included as an initial consideration. Perhaps community involvement and ground-up efforts such as crowd-sourcing will play a role in shaping this new resource.

We’re excited to see how Data.gov will evolve and curious to see how developers and the public utilize the data.

On a related note, the Sunlight Foundation has teamed up with Google, O’Reilly Media, and TechWeb on a new contest for this summer. The Apps for America 2 contest offers a variety of prizes for developers using Data.gov in applications and mashups.