The BEST Instagram Client for your Mac 
View, like, comment, download and share your and your friends’ Instagram pictures on your Mac!!!! And there are even more features!
Of all Mac clients, Instagram allows you to use the most features of Instagram on your Mac and even exceeds instagram’s functionality.
"InstaDesk provides a slick, simple, desktop way to view and appreciate the photos of others." 
http://www.tuaw.com/2011/05/05/tuaws-daily-mac-app-instadesk/ 
Instagram features: 
Know what your friends are up to
View your friend’s feed, pictures, comments, profiles and followers
React to your friends posts
Comment and like pictures
Share pictures on Facebook, Twitter and per Email
Save pictures
Download pictures easily through drag and drop
Save beautiful pictures in albums 
Or Sync your images automatically to a folder 
Receive News and Notifications
See when you get new comments, likes, or followers
Administrate your circle of friends