Does not work anymore with the new last.fm design.
Use this enhanced one instead!

This will also work on international lastfm.* sites.

// ==UserScript==
      // @name lastfmjunkie
      // @description adds btjunkie searching for last.fm artists
      // @include http://www.last.fm/music/*
      // @include http://www.lastfm.*/music/*
      // ==/UserScript==
      
      function lastfmjunkie_search() {
      	var catpage = document.getElementById( 'catalogueHead' );
      	if ( !catpage ) return;
      
      	var heading = catpage.getElementsByTagName( 'h1' )[0];
      	if ( !heading ) return;
      
      	var artistName = new String( heading.firstChild.nodeValue );
      
      	lastfmjunkie_setResults( 'Searching BTJunkie...' );
      
      	GM_xmlhttpRequest({
      		method: 'GET',
      		url: 'http://btjunkie.org/rss.xml?query=' + escape(artistName),
      		onload: function( res ) {
      			if ( res.readyState == 4 && res.status == 200 )
      				lastfmjunkie_displayXml( res.responseText, artistName );
      		}
      	});
      };
      
      function lastfmjunkie_xmlChildValue( node, name ) {
      	var child = node.getElementsByTagName( name )[0];
      	return child ? child.firstChild.nodeValue : '';
      }
      
      function lastfmjunkie_setResults( text ) {
      	var results = document.getElementById( 'lastfmjunkie_results' );
      
      	while ( results.firstChild )
      		results.removeChild( results.firstChild );
      
      	results.appendChild(
      		document.createTextNode(text)
      	);
      	results.style.display = 'block';
      }
      
      function lastfmjunkie_displayXml( xmlText, band ) {
      	var parser = new DOMParser();
      	var xml = parser.parseFromString( xmlText, 'application/xml' );
      	var root = xml.documentElement;
      	var items = root.getElementsByTagName( 'item' );
      	var results = document.getElementById( 'lastfmjunkie_results' );
      	var header = document.createElement( 'h5' );
      
      	lastfmjunkie_setResults( '' );
      
      	header.appendChild( document.createTextNode('BTJunkie Results (first 20)') );
      	results.appendChild( header );
      
      	if ( !items.length ) {
      		results.appendChild(
      			document.createTextNode('nothing found, sorry!')
      		);
      	} else for ( var i=0; i<items.length && i<20; i++ ) {
      		var item = items[ i ];
      		var stitle = lastfmjunkie_xmlChildValue(item,'title');
      		var slink = lastfmjunkie_xmlChildValue(item,'link');
      		var sdesc = lastfmjunkie_xmlChildValue(item,'description');
      		var elink = document.createElement( 'a' );
      		var etext = document.createTextNode( stitle );
      
      		elink.style.display = 'block';
      		elink.href = slink;
      		elink.appendChild( etext );
      
      		results.appendChild( elink );
      	}
      
      	var more = document.createElement( 'a' );
      	more.href = 'http://btjunkie.org/search?q=' + escape(band);
      	more.appendChild( document.createTextNode('see all results') );
      	more.style.fontWeight = 'bold';
      
      	var close = document.createElement( 'a' );
      	close.href = 'javascript:;';
      	close.addEventListener( 'click', function() {
      		results.style.display = 'none';
      	}, true );
      	close.appendChild( document.createTextNode('close') );
      
      	results.appendChild( document.createElement('br') );
      	results.appendChild( more );
      	results.appendChild( document.createTextNode(' - ') );
      	results.appendChild( close );
      }
      
      function lastfmjunkie_run() {
      	var catpage = document.getElementById( 'catalogueHead' );
      
      	if ( !catpage ) return;
      
      	var heading = catpage.getElementsByTagName( 'h1' )[0];
      	var paragraphs = catpage.getElementsByTagName( 'p' );
      	var stats;
      	for ( var i=0; i<paragraphs.length && i<10; i++ ) {
      		if ( paragraphs[i].getAttribute('class')=='stats' ) {
      			stats = paragraphs[i];
      		}
      	}
      	if ( !stats ) return;
      	
      	var title = heading;
      	var link = document.createElement( 'a' );
      	var linkImg = document.createElement( 'img' );
      	var results = document.createElement( 'div' );
      
      	linkImg.src = 'data:image/x-ico;base64,AAABAAEAEBAAAAEACABoBQAAFgAAACgAAAAQAAAAIAAAAAEACAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAgEAAAkFAwAHBQQAGBALACQYEAAoGQ8AOCIVAEIoGAA6ODYAPDo6AD08PABQPjQAQEBAAHpLLQBbTEQAhFExAF1ORgBeU0wAYVRMAIVXOgBlWVIAj2FEAGxkXwB6eXgAfXx8AICAgACphW8ArIp0ALCPegCwkHwAm5SPAKGWjwC4mogAuJyKALqdiwC%2Bo5IAwKaWAMKomADEq5wAxq%2BhAM66rQDQvLAA1MO4ANfGvADYyL4A39LKAODTywDg1MwA4dXNAObb1QDo3tgA5eTjAPDq5gD07%2BwA9fHuAPr4%2BAD8%2BvoA%2FPz7AP%2F%2F%2FwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAADRoaGhoaGhoaGhoaGhoaDRo7Ozs7Ozs7Ozs7Ozs6GhoTJiYmKDE7Ozs7NiYmIDsaCBAQEBAQGzo7OjMQEC47GggQKSweEBAqOgsPEBAwOxoIEDU7ORAQIgsADBAQMDsaCBArLyQQDgQAAAwQEDA7GggQEBAQFAUAAAAPEBAwOxoIECUnFgcAAAALMhAQMDsaCBA1OhICAAALOjMQEDA7GggQIxUAAAAJISMdEBAcIxEIEAYBAAALNxAQEBAQEBAIFy0fAwALOjotLS0tLS0tFxk6GDQLODs7Ozs7Ozs7OxoLADo7Ozs7Ozs7Ozs7OzsaDQoZGhoaGhoaGhoaGhoaDQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA%3D';
      	linkImg.style.border = 'none';
      	linkImg.style.margin = '0px 10px';
      
      	results.id = 'lastfmjunkie_results';
      	results.style.display = 'none';
      	results.style.padding = '5px';
      	results.style.borderTop = '1px #ccc solid';
      	results.style.borderBottom = '1px #ccc solid';
      	results.style.backgroundColor = '#eee';
      	results.style.margin = '5px 0px';
      
      	title.style.float = 'left';
      	link.style.float = 'left';
      	link.href = 'javascript:;';
      	link.addEventListener( 'click', lastfmjunkie_search, true );
      	link.appendChild( linkImg );
      
      	heading.appendChild( link );
      	stats.parentNode.insertBefore( results, stats.previousSibling );
      }
      
      setTimeout( lastfmjunkie_run, 2000 );
      

Good idea. Thanks.