Whenever the new version of SQL Server is released the first thing I search for Books Online update to upgrade the local copy. In similar to that Microsoft have been releasing lot of free resources and tools that can enhance the learning experience for Developers, DBA and Architects. So here are few resources that I would like to refer about R2 product specific:

 

SQL Server 2008 R2 Feature Pack

This R2 Feature Pack is a collection of stand-alone packages which provide additional value for SQL Server 2008 R2. THe important ones I refer:
Microsoft® SQL Server® 2008 R2 Books On-line
    Microsoft SQL Server 2008 R2 Books Online is the primary documentation for SQL Server. Visit the SQL Server 2008 Books Online page on the Microsoft Download Center.

    Audience(s): Developer, DBA



Microsoft® SQL Server® 2008 R2 Upgrade Advisor
    Microsoft SQL Server 2008 R2 Upgrade Advisor analyzes instances of SQL Server 2000, SQL Server 2005 and SQL Server 2008 in preparation for upgrading to SQL Server 2008 R2. Upgrade Advisor identifies feature and configuration changes that might affect your upgrade, and it provides links to documentation that describes each identified issue and how to resolve it.




Microsoft® SQL Server® 2008 R2 Native Client
    Microsoft SQL Server 2008 R2 Native Client (SQL Server Native Client) is a single dynamic-link library (DLL) containing both the SQL OLE DB provider and SQL ODBC driver. It contains run-time support for applications using native-code APIs (ODBC, OLE DB and ADO) to connect to Microsoft SQL Server 2000, 2005, or 2008. SQL Server Native Client should be used to create new applications or enhance existing applications that need to take advantage of new SQL Server 2008 R2 features. This redistributable installer for SQL Server Native Client installs the client components needed during run time to take advantage of new SQL Server 2008 R2 features, and optionally installs the header files needed to develop an application that uses the SQL Server Native Client API.

    Audience(s): Customer, Partner, Developer

You can download the appropriate feature pack that you wanted individually or simply download all of them.

As a part of Self-Service BI feature in SQL Server 2008 R2 you can download the Reporting Services Add-in that is specific for SharePoint 2010:

SQL Server® 2008 R2 Reporting Services Add-in for Microsoft SharePoint® Technologies 2010

The Microsoft® SQL Server® 2008 R2 Reporting Services Add-in for Microsoft SharePoint® Technologies allows you to integrate your reporting environment with SharePoint to experience the benefits of using the collaborative environment provided by SharePoint.

For Developer specific I recommend Microsoft Chart Controls Add-on for Microsoft Visual Studio 2008, Microsoft Chart Controls for .NET Framework Documentation & Microsoft Chart Controls for Microsoft .NET Framework 3.5 that are specific to ASP.NET and Windows Forms Chart Controls for .NET Framework 3.5 SP1. Also on the SharePoint Technologies refer to Microsoft SharePoint Foundation 2010 download.

Finally for entire Visual Studio 2010 related packs refer to List of free downloads to enhance Visual Studio 2010 & SQL Server 2008 R2 knowledge  post.