Another little gallery app I used recently is ThumbGallery from FlashRelief. It’s $20, but that’s really cheap considering how nice this gallery is. You don’t need Flash at all–they provide you with a pre-compiled Flash control which you embed into a web page, and you configure the whole thing with a simple XML file. Downside is having to make both a thumbnail and full size image yourself, which can get tedious if you have a lot.
We used this recently on our prom corsage and boutonniere gallery at http://www.bloomery.com/promgallery.htm.