The Native Instruments Komplete Kontrol software has a Scale mode which can be used to automatically indicate, map or form chords from the notes in a given musical scale. There is a large number of available scales from the most common to some that are truly obscure. If you know the scale you want you can just dial it up but, if your knowledge of all of these scales is limited, it can be difficult to find the scale that suits your needs.
The software presented here is designed to at least partially alleviate that problem.
The Scale Finder Software
This software allows the user to select a collection of pitch classes, with or without a nominated tonic note, and presents all of the scales which contain those notes and, if they exist, those scales which contain only those notes.
So, if you are playing around with a melody and are not sure of which scales might suit is for either extension or harmony purposes you can enter all of the pitch classes from the melody into this software and it will give you the scales which match.
In the image above, the white keys are selected and the application identifies that the scales,
are exact matches for the chosen pitch classes and that the scales,
contain all of the chosen pitch classes but also extra notes.
Clicking on one of the scales in this second list will cause asterisks to appear next to all of the pitch classes contained within the chosen scale.
This software is available to download here for various platforms.