If you have an iPhone, you HAVE to check out this app. It doesn't have as many filters and bells/whistles as Hipstamatic which I kind of like. The down side is that the built in camera in the app doesn't create a very big file so if you are wanting to print your Instagram photo later, it probably won't go very well. Although, I just got a note from Blurb books that they have an upload program to instantly make a book out of your Instagram photos.
Here are some of my Instagram photos from the last 2 months. I even took some photos at a friend's wedding where I was a guest. Definitely makes you think out of the box when all you have is your iPhone to make a great photo at a wedding!
Enjoy!