Sheet Lightning is a specialised engineering 2D/3D CAD System for creating and unfolding sheet metal designs for fabrication or manufacture. It handles everything from simple cylinders, cones, rectangular ducts and ovals, to adapters, adapting any of these section types, interections and multi-intersections between of any of these types to any level of complexity.

CopanMobile for PocketPC
CopanMobile for PocketPC allows you to COGO (coordinate geometry), process field surveys, adjust map traverses, perform map/deed checks, calc curves and areas/perimeters, transform coords, interface with GPS, and import/export Ascii files. It's free.

Turbine
Calculate turbine steam consumption and exhaust steam conditions. Built-in steam properties. Wide variety of units of measure included.

Copan Pro
Copan Pro enables you to calculate coordinate geometry (COGO), process field surveys, adjust map traverses, perform map/deed closure checks, calculate areas and perimeters, transform coordinates, import/export Ascii files, and draw lines and symbols.

Exfilt
Quickly and easily design or analyze stormwater detention ponds and below grade systems for exfiltration/infiltration. Design stormwater systems to meet exfiltration volume drawdown time criteria.

Uconeer
Freeware. 390 units in 46 categories. Includes engineering specific categories like enthalpy, heat capacity, heat transfer coefficient, torque and viscosity. Work with feet and inches. Formatting and clipboard features. Excludes archaic units.