Unity natively imports Blender files. This works under the hood by using the Blender FBX exporter.
To get started, save your .blend file in your project’s Assets folder. When you switch back into Unity, the file is imported automatically and will show up in the Project View.
To see your model in Unity, drag it from the Project View into the Scene View.
If you modify your .blend file, Unity will automatically update whenever you save.
See Using Blender and Rigify for more details of how to import animated, boned characters into Unity for use with Mecanim.