If you love taking photos, you're going to love Photo fx ($2.99, available here), the most impressive photo filter app yet. It creates simulations of many popular, award-winning Tiffen glass filters, optical lab processes, and photographic effects. The 26 filters here are organized into five categories, so they're easy to navigate. When you've found one you like, you can customize the appearance with on-screen sliders. If you don't like what you've done, give your iPhone a shake to reset the controls.