Sagulator helps you design shelves by calculating shelf sag (deflection) given type of shelf material, shelf load, load distribution, dimensions, and method of attachment
optiCutter offers free calculators for optimizing cut layouts on both linear material and sheet goods
Like optiCutter, CutList Optimizer is a handy tool for creating cut layouts on sheet goods.
Woodworkers' Source includes a board foot calculator to help you figure out how much material you need and how much it will cost.
Blocklayer's calculator for kerf bending helps you determine the optimal spacing between kerfs to bend wood to a specific radius.
Free digital design tool that generates dimensioned built drawings for stick chairs, casework, and some joinery.