Changemon is a little tool I wrote to quickly check differences between copies of folders that may have changed. It can also monitor a folder and list files as they are added, changed and removed.
Examples:
$ changemon.py -c ./a ./b --flags "ar"
Added
-----
Removed
-------
s
The files that have been added and removed in folder b.
$ changemon.py -c ./a ./b
Added
-----
Changed
-------
greet
t
z
Removed
-------
s
The typical summary.
$ changemon.py -c ./a ./b --flags "u"
Unchanged
---------
zerobyte.txt
nochange.txt
The files that haven't changed in either folder.