I first noticed this app on Reddit which has become the home for internet memes.
Michael Fogleman is offering iMeme as a free download. The app is designed for Mac OS X.
It allows you to create your own memes based on the popular ones on the web.
The user interface is as simple as it can get. And there are options to upload the generated images on Imgur. Once the image is generated it can also be automatically submitted to Reddit.
If you notice a meme attack on Reddit, you can blame this app for that!