I just noticed that MSDN posted a ton of SharePoint 2013 code samples on their site... you can find them here: http://code.msdn.microsoft.com/officeapps
I contributed a few to this list, specifically around SharePoint 2013 Windows Azure Workflow:
- SharePoint 2013 workflow: Call an External Web Service - this one shows how to create a workflow in Visual Studio 2012 that calls a web service using the new HTTP activities and the DynamicValue data type.
- SharePoint 2013 workflow: Create a Custom Action - this is the same thing as above, but I moved the web service call to a custom action for use in SharePoint Designer 2013 or Visual Studio 2012 workflows.
Both samples have been republished to work with RTM. See this post for more information.