Digital Scale

This is a handy item to have in the kitchen if you're doing much in the way of food preservation or large batch cooking (and actually, it's handy even for regular cooking). I have this one, but they are made by a variety of companies at a variety of price points. Mine will give weights up to 11 pounds and has a digital display with options for ounces, pounds, grams, and kilograms. It also has a tare option, which is great: put a container on the scale before turning it on and it will zero out the container's weight; or put the container on and hit the tare button.

Not only does the scale allow me to measure precise quantities to either follow recipes or record the amounts used in the ones I develop myself, it is also great for packaging food in uniform quantities for the freezer - and being able to add the weight to my labels so I know later how much I've got.