codespell (spell checker for source code)

codespell fixes common misspellings in text files. It's designed
primarily for checking misspelled words in source code, but it can be
used with other files as well.

Optional dependency: python-chardet. This is required for codespell's
-e option. Unless you deal with files that are not ASCII, ISO-8859-1,
or UTF-8, you probably don't need the -e option.