How much is a George Washington 1 cent stamp worth?

The US has issued many stamps with George Washington of many different values, including a number of 1 cent values. And if it is unused, you can always use it for 1 cent postage. You will need to consult the catalogs and do some research. There are lots of stamps issued and they vary in value from almost nothing to some nice values.

Most libraries will have a copy of Scott's Postage Stamp Catalog of the World. First of all, you have to identify the specific stamp or card. That in itself can be a daunting task, but most of the catalogs are well illustrated with lots of information. Once you know what item you have, the catalog will provide a set of prices that can be used to estimate value.