Several Web sites offer RSS feeds, but they do not necessarily cover the type of information you are looking for, and there aren't many tools to check local files.
Changes Meter does this exact job for you and it will notify you with a colorful, useful, and unobtrusive pie-chart icon on the menu bar.
- Now requires at least OS X Lion 10.7.5
- Added support for OS X Mavericks 10.9
- Added support for importing and exporting the roster
- Replaced the page comparison algorithm with a much improved one
- Updated Growl support