A function that allows other functions to be called only one time per page load.

once.js

function once(fn, args, unique){
	if ( typeof onces === 'undefined' ){
		onces = {};
	}

	if ( typeof fn === 'function' ){ //If the first parameter is a function
		if ( typeof args === 'string' ){ //If no parameters
			args = [];
			unique = args;
		}

		if ( typeof onces[unique] === 'undefined' || !onces[unique] ){
			onces[unique] = true;
			return fn.apply(this, args);
		}
	} else { //Else return boolean
		unique = fn; //If only one parameter is passed
		if ( typeof onces[unique] === 'undefined' || !onces[unique] ){
			onces[unique] = true;
			return true;
		} else {
			return false;
		}
	}
}

Careful, onces becomes a global var.