The Neckar River region is beautiful, and it contains some really decent and interesting castles, especially since it is not as heavily traveled as some other areas of Germany.  The castles listed here do not cover all along the river, and some have even just a few photos.  However, so far the ones visited have proven to be excellent examples of castle design. 

The river is overall peaceful, but still sports the occasional tour boat.  The one captured below left is clearly heavily loaded, as it has almost no freeboard!  The insets below demonstrate the quality of the Sony A100 at 10 megapixels.  The first is a group on the foc'sle of the boat, while the second is amid ship.  It's funny to see a guy on the boat taking a photo of me even as I snapped his!

I currently have plans in the works to go back and finish research on several other castles in the area.