Interesting enhancements for Microsoft Flight Simulator X:

• FSX European Ground Textures Package by Adam Mills
  Intended to solve three common complaints with European textures: the "desert" problem, winter textures and autumn textures. These modified textures reduce or eliminate the barren brown color of the default textures and improved the drab washed out fall and winter colors too.
  Part 1-8 at Simviation
  
• FSX Digital Elevation Model for Alps region by Alain Ragot
  FSX Scenery--Mesh Alpes LOD11 V2. Covers French Alps and parts of Switzerland, Italy, Austria, Germany and Slovenia
  (LOD11) Mesh Alpes LOD11 V3
  
  
• FSL_TextureFix_V1.0.zip
  http://forums.flightsimlabs.com/index.php?/files/file/66-fsl-texturefix-v10zip/
  brilliant new FSX tweaks to improove frame performance
  (also relevant to get better result for the openVFR POI Addons)
  
  
  
• Mogwaisoft - Shade for FSX
  http://www.flightsimstore.com/product_info.php?products_id=1894
  Shade is a small program that allows you to setup custom colours/tones schemes for FSX's 3d/Terrain lighting/shadow & Fog values this allows you to alter the contrast between light and shadow tones within FSX allowing for creation of more realistic lighting conditions with much better definition/contrast.

These projects are also using Openstreetmap data in their sceneries:

• Xplane – OSM scenery (X-VFR)
  http://xvfr.beomuex.org/
• Flightgear – OSM scenery
  http://gallery.flightgear.org.uk/c1483094.html
• Microsoft FSX  – OSM scenery for Denmark
  http://www.jkelloggs.dk/scenery/denmarkmapx