Open Data Protocol is a Web protocol for querying and updating data that provides a way to unlock your data and free it from silos that exist in applications today. There're already several OData producers like: IBM WebSphere, SQL Azure, SQL Server Reporting Services; and live services like: Netflix or DBpedia among others. SharePoint 2010, is an OData provider as well and this enables Access Services as an OData provider as well. In addition, clients across many platforms, ranging from ASP.NET, PHP, and Java websites to Microsoft Excel, PowerPivot, and app on mobile devices, are finding it easy to access those vast data stores through OData as well.
SQL Azure OData Service incubation (currently in SQL Azure Labs) provides an OData interface to SQL Azure databases hosted by Microsoft. Currently SQL Azure OData Service is in incubation and is subject to change. The main protocol to call SQL Azure is Tabular Data Stream (TDS), the same protocol used by SQL Server.