ArcGIS.com includes a cool website, but as we learned when developing the Geoportal Extension, it also provides a RESTful interface. This meant we could offer users of the Geoportal Extension access to the information others are sharing through ArcGIS.com.
In the Geoportal Extension we allow distributed searches to go to ArcGIS.com. We implemented this early on in our contribution to the Group on Earth Observation
Realizing that many organizations aren't waiting for yet another portal, we developed a simple mechanism to integrate a search widget into any web page that would allow searching Geoportals. This has resulted in an HTML widget that can be embedded with 2 simple lines of HTML. By default this widget searches the Geoportal it is part of. But hold on, there's more!
The Geoportal can search external catalogs, including ones that implement the Open Geospatial Consortium (OGC) Catalog Service for the Web (CS-W), but since 9.3.1 it can also search... ArcGIS.com! Try it at the GEO Portal by going to the search page and selecting ArcGIS.com from the 'search in' dialog. You'll notice it searches ArcGIS.com with the keywords you give. This means any Geoportal 9.3.1+ is a client to ArcGIS.com.
But back to the widget.
Directing the searches from the widget to ArcGIS.com is possible by adding a parameter that instructs the Geoportal to direct the searches to the identified remote site. And thus here is a widget that searches ArcGIS.com. All it took was a minimal HTML like this:
src="http://geoss.esri.com/geoportal/widgets/searchjs.jsp?rid=ArcGISOnline" > </script>
Using these lines you could embed ArcGIS.com searches in your own web page. Using this approach, you could build your own ArcGIS.com client. Take a look at databasin.org for a more sophisticated example.
To learn more about the options for the widget, visit the Geoportal Extension help pages.
PS: At version 10, the Geoportal will support federating searches to more than one remote catalog and also include ctalogs of non-structured metadata or even non-spatial content, such as Wikipedia, Flickr, YouTube, or your document management system. Try out the weekly release of Geoportal 10 at out public sandbox. Let me know if you find any issues. We are wrapping up development, but we're open to your feedback.