Almost every blog in the world now has lightbox-style photo capabilities, except mine. :-( What I'd like is the ability to add a photo (or a "gallery", i.e. a set of photos), have them appear as thumbnails, then expand to full size when clicked - without navigating away from the page. For galleries, you should be able to click one side of the expanded image or the other to see the next or previous photo.
Let me know if I can provide links to some of the millions of examples of this out there.
Photos are a big reason for blogging - please spend some time enhancing this.