Spatial thinking has always been important for art, architecture, design, aeronautics, mathematics, computers, science, surgery, and engineering, but it's also a preferred mode of thinking or reasoning for many inventive people in "non-spatial" disciplines.
Here are links to a good introductory Powerpoint on Spatial Literacy. the National Academies Press also has a free online book Learning How to Think Spatially. Research studies show that didactic instruction can improve scores on spatial tests, but most spatial experts recall their most valuable early education coming from hands-on hobbies or mentoring by a spatially talented individual.
Inc.com's 2005 Entrepreneur of the Year was the very spatial Ping Fu, who attended no school at all from age 7 to 18 (see link below). She is now CEO of GeoMagic, a company that dominates the high tech field of digital shape sampling and processing, or DSSP. This technology allows high resolution scanning with optical beams with complete rendering in 3D fidelity for anything from NASCAR cylinder heads to parts of an artificial heart. They've even scanned in the Statue of Liberty.
Nat' Academies Press, Learning to Think Spatially: GIS as a Support System in the K-12 Curriculum (2006)
Spatial Literacy Powerpoint
Ping Fu Spatial CEO & Entrepreneur of the Year