Little trick to check if a gravatar is available or not for a certain email address.

gravatar.js

var http = require('http'),
	md5 = require('MD5');

var options = {
	method: 'HEAD', 
	host: 'www.gravatar.com', 
	port: 80, 
	path: '/avatar/' + md5('info@blabla.be') + '?d=http://bla.com'
};
var req = http.request(options, function(res) {
	if( res.headers.hasOwnProperty('location') ) {
		console.log('No gravatar available');
	} else {
		console.log('Gravatar available');
	}
});
req.end();