You might be surprised at some of the cool samples that are included in the Revit SDK – which is likely already installed on your system.  Here are a few notes on pathing that may assist:

Build Revit API Samples:
C:Revit 2014 SDKSamplesSDKSamples2014.sln

Copy these files

to
C:Program Files (x86)Reference AssembliesMicrosoftFramework.NETFrameworkv4.0

Build solution

Modify DLL path in:
C:Revit 2014 SDKSamplesRvtSamplesCSRvtSamples.addin
to
C:Revit 2014 SDKSamplesRvtSamplesCSRvtSamples.dll

Save the .addin to:
C:ProgramDataAutodeskRevitAddins2014