Use ajaxSubmit to post to more than one channel in ExpressionEngine (EECMS) with Safecracker

form_template.html

<!-- first form -->
{exp:safecracker id="form1" json="yes" channel="channel1" include_jquery="no" 
			return="safecracker/ENTRY_ID" 
			safecracker_head="no"}

Title: <input type="text" name="title" value="{title}" />

{/exp:safecracker}

<!-- second form -->
{exp:safecracker id="form2" json="yes" channel="channel2" include_jquery="no" 
			return="safecracker/ENTRY_ID" 
			safecracker_head="no"}

Title: <input type="text" name="title" value="{title}" />

{/exp:safecracker}

<!-- our submit "button", note the "onclick" if I used jQuery to wire the event, it would submit twice! weird...if someone can get this to work without "onclick" let me know! -->
<a href="#" onclick="return submitForms();" id="submitforms">Save Changes</a>

<script type="text/javascript">
function submitForms() {
	//disable button to prevent double submits
	$('a#submitforms').attr("disabled", "disabled");
	
	/* first submit */
	postAjaxSafeCracker($('#form1'), function(data) {
		if(data.success == 1) {
			/* second submit, data.entry_id can get you the entry_id of the first channel entry you save */
			postAjaxSafeCracker($('#form2'), function(data) {
					if(data.success == 1) {
						/* redirect or do something else */
						alert('both submitted!');
					}		
			});
		}
		
		$('a#submitforms').removeAttr("disabled");
	});
	
    return false;
}

/* utility function to easily submit the form, requires http://jquery.malsup.com/form/ */
function postAjaxSafeCracker(elem, success) {	
	$(elem).ajaxSubmit({
		type: "POST", 
		dataType: "json",
		iframe: true,
		success: success,
		error: function(xmlRequest, textStatus, errorThrown) {
			alert(errorThrown);
		}
	});
}
</script>		

BTW, make sure you include jQuery in your header (or you can use safecracker's...personally I prefer to use my own)