I released my first node.js module today on npm, aptly named stalker. stalker is basically a wrapper around fs.watchFile(). It will watch a directory tree for new files and fire off your callback whenever it finds one. It tries to be smart about entire nested folder/file structures and tricksy add/removal/add type of stuff.
Get it on npm: npm install stalker
You can test it by running node example/test.js and then dropping files and folders in the example directory.
To incorporate it in your program, simply call stalker.watch with your callback:
stalker.watch('/var/foo', function(err, file) {
console.log('stalker saw file %s', file);
});
Code is at github: https://github.com/jslatts/stalker