For many people, the biggest challenge with digital photography is finding the images after you've uploaded them. A surprising number of people use no organized method of storing their images, making it difficult to find what you're looking for among thousands of files that typically have nondescript names like IMG_2001.JPG or something similar. And, this often leads to have many copies of the same image cluttering up your drive.
This is the person Snapselect was designed for. Snapselect is a Mac only app, as you might expect from a company named Macphun. An affordable option ($14.99), using a patented image recognition method, Snapselect will automatically group similar images together, selecting the images you want for sharing or editing, and deleting the unwanted shots.
You can either work with images already on your computer, or you can import directly from a memory card. This is actually a better option if you have an organized library, with your images grouped by similarity - handy if you've shot a couple of dozen images of the same subject and only want to import two or three of them.
Importing images is fast. You can also work with libraries from iPhoto, Aperture, Lightroom, or just folders of images. While the importing is fast (I was able to import several thousand images in just a few minutes. Building thumbnails and analyzing them for similarities took quite a bit longer, perhaps an hour in total on my MacBook Pro Retina. The default option is Normal accuracy and infinite in time, so if you have a source image you took three years ago along with a copy you edited yesterday, Snapselect will group them together. Unfortunately, if you want to change the accuracy settings, Snapselect has to go through the entire process of analyzing them again. This is not the case for the time setting which is very quick.