I just stumbled on this app that happens to be free right now and I think its worth a look.
I’m really not a filter photographer, but I thought I would give this app a try since its free. I like that you can choose a filter/preset and then modify the settings, so there is still room for you to be involved in the creative process. You can save your own presets for future use, and you can download some more for free.
The tool that stands out to me upon first use is the vignette. A lot of app developers have no clue how to make a professional looking vignette, but these guys did a solid job. It seems like a lot of the adjustments are actually useful if you know how to use them.