Video tutorials by user Mikael
His YouTube page: here (youtube name: aramakara)
Lightmapping with Blender, export to Ogre
Creating a simple scene with Blender
Creating a heightmap with Blender
Using Inkscape and Blender
Level creation tutorials by user Nikki:
Many videos about level creation with Blender.
(Currently videos from vimeo.com can't be embedded to this wiki.)