Carousel from Mobelux isn't the first Instagram client for the Mac, but it is one of the most elegant. The program culls your Instagram feed and streams these images to your desktop in a gorgeous UI that resembles an old-fashioned photo album.
Three buttons along the bottom toggle your view among current favorites, your feed and your photos. On each image, you select a person's avatar to see their profile, like the image by clicking on a heart or add a comment by clicking on the word bubble. You can save images by dragging them to iPhoto or saving through the drop-down menu.
Carousel features a number of keyboard shortcuts that expands usability of the app, but you can only view pictures, not upload them from your Mac. You also can't search for other Instagram users, photos or tags at this point, which is a drawback. You'll have to do this all from your iPhone. You also can't resize the window below a certain point, which means it takes up a good chunk of smaller screens, such as on a MacBook Air.
But, Carousal does a brilliant job at displaying the best that Instagram has to offer. It reminds me that I clearly don't use the app enough, and it's amazing to go through the popular feed and see the gorgeous photography people have shot using Instagram.