ArcGIS.com is ESRI's online repository for GIS data. It includes maps and data published both by ESRI and the GIS community. Using ArcGIS.com is free. You can access online basemaps and downloadable data. You can also use ArcGIS.com as a repository for maps and data that you want to share with others. You can upload and share your maps and data with everyone, or just with the members of private groups.
ArcGIS.com is built into ArcGIS 10. You can access maps and data in ArcGIS.com, upload maps and data to it, and manage your ArcGIS.com account entirely from within ArcGIS Desktop without having to launch a Web browser or know which Web sites to visit. You can launch the new ArcGIS Online dialog box in ArcMap with the File > ArcGIS Online command. You can also launch this dialog box using the new Add Data From ArcGIS Online command with the Add Data menu button on the Standard toolbar:
This dialog box lets you browse and search for maps and data. In ArcGIS.com, you can find map services (live maps being served via ArcGIS Server); layer packages (LPK files); and map packages (MPK files), which are new in ArcGIS 10. You can also search for groups, which are collections of items, and browse their content. ArcGIS.com groups are created by particular organizations, project teams, or interest groups. The data in groups may be accessible to all or restricted to members of the group.
You can sign in to your ArcGIS.com account, or create an account, using the File > Sign In command or the Sign-In link on the ArcGIS.com dialog box. By signing in, you'll be able to create and join groups and access maps and data in any private groups you belong to. You'll also be able to upload your own data into ArcGIS.com and share it with others. For example, suppose your agency is involved in a project with several other agencies. You can create an ArcGIS.com group for this project and invite people from those agencies to join it. All members of the group can upload data into it and choose whether their data will be available publically or only to other members of the group.
In addition to being able to search ArcGIS.com via the dialog box shown above, you can also search ArcGIS.com using the new Search window in ArcGIS Desktop. The Search window, described in What's new in ArcMap basics at 10, puts all of ArcGIS.com at your fingertips in a convenient dockable window. For example, you can use it to search for particular data on your local system, then extend that search out to ArcGIS.com.
Layer packages (LPK files) were introduced in ArcGIS 9.3.1 to make it easy to share data with others. A layer package combines a layer file and the data source it references in one easy-to-use file. Layer packages have been improved in ArcGIS 10 including more complete validation of layers that you package to ensure that they work correctly when they are unpacked. Layer packages created in ArcGIS 10 can be shared with people using 9.3.1 or 10. You can also create layer packages that just contain the schema of the data they reference, which can then be used by others as templates for creating new datasets using the layer properties, such as symbology, and schema of your original layer.
When you right-click a layer, group layer, or set of selected layers and choose Create Layer Package, you get the option to immediately upload the package into your ArcGIS.com account and choose how it will be shared.
Map packages (MPK files) make it easy to share complete map documents with others. A map package contains a map document (MXD file) and the data referenced by the layers it contains, packaged into one convenient, portable file. Map packages can be used for easy sharing of maps between colleagues in a work group, across departments in an organization, or with any other ArcGIS users via ArcGIS.com. Map packages have other uses, too, such as the ability to create an archive of a particular map that contains a snapshot of the current state of the data used in the map. To create a map package, use the new File > Create Map Package command in ArcMap. Before packaging a map, be sure to enter descriptive information about it in the File > Map Document Properties dialog box. This information is built into the package and is accessible to others when you upload your map package into ArcGIS.com.