The Brain Maps API
BrainMaps.org has recently implemented a new AJAX-enabled multiresolution image viewer. Though a bit skimpy on functionality compared to the heavy-weight Flash viewers, it is snappy fast, uses very little memory, and in principle, allows for better integration with other HTML entities through DOM. An example is at http://brainmaps.org/ajax-viewer.php?datid=95&sname=123
What's more, the multiresolution viewer has been released as the Brain Maps API. The following is from the Brain Maps API page:
An example of the new Brain Maps AJAX GUI, which is a more beefed-up version of the Brain Maps API, is shown below:
Try going to this link to see what all the fuss is about, and once there, try clicking and dragging the image, or clicking on the little tree icon in the upper right. Also, the mouse scroll wheel should zoom you in and out.
Google Maps for the Brain? Not quite yet. It still needs image overlays and labels. But that being said, it's the best I've seen yet.