Following del.icio.us' release of JSON output for URL lookups, here's an update to Jon Udell's memetrack script that displays how many people have tagged the current page: →metrack←. It eval's the JSON response, so decide if you trust the Yahoo/del.icio.us servers enough not to return malicious javascript. At the moment it's set up for this site, so you'll need to edit the includes and the insert variable for your own site as appropriate.
Of course, you could always use the official badges, if you want everyone to see the results.