It’s not often that you get genuine joy out of using an app on the iPhone/iPad, but [Camera+](http://campl.us/) is one of them. I needed something to reinvigorate my interest in photography, and Camera+ is really helping with that. Not only is a competent camera, the filters and effects provided are simple to use and produce some great results. I’m particularly loving the ‘Clarity’ filter, which adds some real pizzaz to images.
I’ve always enjoyed a slightly (or even extremely) unnatural colour and/or saturation effect on images, and Camera+ saves a huge amount of fiddling around later in Photoshop.