Conditionally load jQuery (with slight version independence). Not expecting the API to change a whole lot in the sub-versions.

conditionally-load-jquery.js

//Conditionally load jQuery
//inspired by http://www.smashingmagazine.com/2010/05/23/make-your-own-bookmarklets-with-jquery/

window.onload = function () {
    if (typeof jQuery == 'undefined') {
	var jQ = document.createElement('script');
	jQ.type = 'text/javascript';
	jQ.onload = jQ.onreadystatechange = myOnLoadEvent;
	jQ.src = 'http://ajax.googleapis.com/ajax/libs/jquery/1.5/jquery.min.js';
	document.body.appendChild(jQ);
    } else {
	myOnLoadEvent();
    }
};

function myOnLoadEvent() { 		
	jQuery(document).ready(function($) { 
		alert('your code here');
	});
}

jQ.onload was not referencing a real function.