Windows only: TheFolderSpy is a freeware application that monitors defined files and folders on your PC, but can also run a program when a change is detected in the specified folder.
TheFolderSpy is a super-lightweight program that monitors and alerts the user if files are changed, added or deleted within a folder. The small, portable program monitors every file in the folder or can be filtered to monitor only certain types of files within it. TheFolderSpy also can execute or run a program when a change is detected within a file. (For instance, Ghacks suggests that when a temporary directory is changed, a temporary cleaner can be set to run automatically to clean the folder.)
The program can log and save all the changes made, but unfortunately there's no option to automatically save all changes to a file. TheFolderSpy is a free download for Windows only.