Aphoto:-
aPhoto uses a gesture-based user interface for editing and enhancing photographs. It can be used for basic colour and brightness adjustments or to add effects and filters like vignetting, rainbow, white glow, pencil, emboss and lithograph. A useful 'borders' option shows you how the photo would look with photoframes of different shapes. With a simple in-app purchase, you can add the option to write rich text on the images to create photo greeting cards and emails.
Pho.to Lab:-
Pho.to Lab is great if you want to create fun montages, collages, contact icons or phone wallpapers. It includes over 450 different photo effects, filters and also features intelligent face detection that automatically adjusts and places a person's face onto a montage. Once you're done, the edited image can be stored on the phone or shared directly to various social networks. Pho.to Lab is also available as a free online photo editor and for Android devices.
Adobe Photoshop Express:-
Adobe's Photoshop Express allows you to crop, rotate and flip photos, add borders, filters, effects as well as adjust color, saturation and contrast. It also offers an Adobe camera pack for the iPhone (paid for via in-app purchase). The camera pack lets you reduce noise in camera images as well as set a timer. If you choose to create a free photoshop.com account from within the app, Adobe gives you 2GB free cloud storage to store your photos and videos.