a jQuery (v1.8.1) plugin which uses data-* attributes to unobtrusively trigger ajax calls.

jquery.AT.autoXHR.js

/**
 * @package javascriptApp
 * @author Adrian Testa-Avila <AT@custom-anything.com>
 * @copyright 2012 Adrian Testa-Avila
 * @license Creative Commons Attribution-ShareAlike 3.0 Unported 
 *   <http://creativecommons.org/licenses/by-sa/3.0/>
 */
 
/**
 * jQuery plugin: AT.autoXHR
 * uses HTML5 data-* attributes to inobtrusively trigger ajax calls.
 * @uses jQuery version 1.8 <http://jquery.com>
 */
(function( $ ){
	$.fn.autoXHR = function( userOptions ){
		console.log('autoXHR: setting event listeners');
		var options = {
			 data_autoXHR: 'data-autoxhr'
			,data_XHRinto: 'data-xhrinto'
			,triggerEvent: 'click'
		};
		if( userOptions ){ $.extend( options,userOptions ); }
		return this.each( function(){
			var listener = this;
			$( this ).on(
				options.triggerEvent
				,'['+options.data_autoXHR+']'
				,function( event ){
					console.log('autoXHR: triggered');
					event.preventDefault();
					
					var triggerData = (function( t ){
						var d = t.attr( options.data_autoXHR );
						try{ d = JSON.parse( d ); }catch(e){ /* no error, just not JSON */ }
						var tD = { args:'',complete:'',resource:'',success:'',target:'' };
						if( typeof d === 'object' ){ $.extend( tD,d ); }
						else if( typeof d === 'string' ){ tD.resource = d; }
						// set resource
						if( !tD.resource || /^#/.test( tD.resource ) ){ 
							h = t.attr( 'href' ) || '';
							tD.resource = h + tD.resource; 
							if( !tD.resource ){
								console.log('autoXHR: trigger specifies no resource');
								return false;
							}
						}
						// set container
						if( tD.target == '' ){
							tD.target = t.closest( '[' +options.data_XHRinto+ ']' );
							if( !tD.target || !tD.target.length ){
								tD.target = listener.children( '[' +options.data_XHRinto+ ']' );
								if( !tD.target || !tD.target.length ){
									tD.target = $( listener );
								}
							}
						}else{ tD.target = $( tD.target ); }
						if( !tD.target || !tD.target.length ){
							console.log('autoXHR: target container invalid or not specified');
							return false;
						}
						// set success handler
						switch( tD.success ){
							case 'html':
							default: 
								tD.success = function( response ){
									tD.target.html( response );
									console.log('autoXHR: successful');
									event.preventDefault();
								}
								break;
						}
						return tD;
					})( $( event.target ) )
					
					$.ajax({
						 'data'		: triggerData.args
						,'global'	: false
						,'success'	: triggerData.success
						,'url'		: triggerData.resource
					});
				}
			);
			console.log('autoXHR: ' +options.triggerEvent+ ' listener set');
		});
	}
})( jQuery );

rewritten. documentation forthcoming.

This has actually been updated and put in my front-end repo at https://github.com/customanything/front-end-lib/blob/master/jQuery/autoXHR.0.2.js

I'm interested in it again - got some feedback; I'll be rewriting it a bit; breaking some procedural stuff off into functions.