Administration - Military personnel skills, procedures, duties, etc.

Advancement - Military career advancement books, etc.

Aerographer/Meteorology - Meteorology fundamentals, atmosphere physics, atmospheric phenomena, etc.
Navy Aerographer and Meteorology Manuals

Automotive/Mechanics - Automotive maintenance manuals, diesel and gasoline engine mechanics, automotive parts manuals, diesel engine parts manuals, gasoline engine parts manuals, etc.
Automotive Accessories | Carrier, Personnel | Diesel Power Generators | Engine Mechanics | Filters | Firetrucks and Equipment | Fuel Pumps and Storage | Gas Turbine Generators | Generators | Heaters | HMMWV (Hummer/Humvee) | etc...

Aviation - Principles of flight, aircraft construction, aircraft hardware, aircraft power plants, aviation parts manuals, airplane parts manuals, etc.
Navy Aviation Manuals | Aviation Accessories | Aviation General Maintenance | AH-Apache Helicopter Manuals | CH-Series Helicopter Manuals | Chinook Helicopter Manuals | etc...

Combat - Service rifle, pistol marksmanship, combat maneuvers, organic support weapons, etc.
Chemical-Biological, Masks, and Equipment | Clothing and Individual Equipment | Combat Engineer Vehicle | etc...

Construction - Technical administration, planning, estimating, scheduling, project planning, concrete, masonry, heavy construction, etc.
Navy Construction Manuals | Agregate | Asphalt | Bituminous Distributor Body | Bridges | Bucket, Clamshell | Bulldozers | Compressors | Container Handler | Crusher | Dump Trucks | Earth Movers | Excavators | etc...

Diving - Diving and salvage manuals for miscellaneous equipment.

Draftsman - Fundamentals, techniques, drafting projections, sketches, etc.

Electronics - Electronics maintenance manuals for Basic repair and fundamentals. Computer parts manuals, electronic component parts manuals, electrical parts manuals, etc.
Air Conditioning | Amplifiers | Antennas and Masts | Audio | Batteries | Computer Equipment | Electrical Engineering (NEETS) (Most Popular) | Electronics Technician | Electrical Equipment | Electronic General Test Equipment | Electronic Meters | etc...

Engineering - Drafting fundamentals and techniques, drafting projections and sketches, wood and light-frame construction, etc.
Navy Engineering | Army Costal Inlets Research Program | etc...

Food and Cooking - Manuals for recipes and food preparation equipment.

Logistics - Logistics Data for millions of different parts.

Mathematics - Arithmetic, elementary algebra, pre-calculus, introduction to probability, etc.

Medical Books - Anatomy, physiology, patient care, first aid equipment, pharmacy, toxicology, etc.
Navy Medical Manuals | Agency for Toxic Substances and Disease Registry

MIL-SPECs - Government MIL-Specs and other related material

Music - Major and minor scale activities, diatonic and non-diatonic melodies, time beating patterns, etc.

Nuclear Fundamentals - Nuclear energy theories, chemistry, physics, etc.
DOE Handbooks

Photography & Journalism - Theory of light, optical principles, light sensitive materials, photographic filters, copy editing, writing for publications, etc.
Navy Photography & Journalism Manuals | Army Photography Printing and Journalism Manuals

Religion - Major religions of the world, worship support functions, chapel weddings, etc.