The japanese program Toycamera AnalogColor is certainly among my top 3 apps.
The program gives you a wide and very nice spectrum of vintage color effects you can also choose the framing. If you want polaroid framing no problem. I especially love the cover open feature. The program is is easy to use ( just drag and drop).  You can buy it for 9.99 through their website or just check the blog to see some samples .