Freeware. 390 units in 46 categories. Has all basic categories and engineering specific categories like enthalpy, heat capacity, heat transfer coefficient, moment of inertia, surface tension, torque and viscosity. Converts feet and inches to and from decimal lengths. Converts between dynamic and kinematic viscosity. Steel hardness equivalents. Gas Constant in 900 sets of units. Excludes archaic units. Powerful formatting and clipboard features.

AlcoDens
Convert density of ethanol-water mixtures to and from concentration expressed in Mass, Volume or Molar terms. Covers concentrations from 0% to 100% and temperatures from 10C to 100C. Calculate blending ratios based on source or blend properties.

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.

Sheet Lightning
Sheet Lightning is a specialised engineering 2D/3D CAD System for creating and unfolding sheet metal designs for fabrication or manufacture. It handles cylinders, cones, square-to-round adapters, ovals, intersections and mutli-intersections.

BeamBoy
BeamBoy is a free engineering utility for calculating stress and deflection of structural beams under load. May also be used for shafts. BeamBoy is menu-driven and intuitive.

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.