I posted about the Camera Awesome app made by Smugmug before. It is a very useful app if you want to take your iPhone photography to the next level. In addition to the free app you can purchase additional effects and filters via an in-app purchase. Usually that’s $10 but now it is on sale. You can get the whole set for about $1. I am using camera awesome as my main photo app.
Download it for free (with limited effects and filters), try it out and upgrade for $1 (usually $10) until the 9th of September. Definitely worth a try.