I do not have an iPhone. This isn't a fact that would bother me were it not for one thing: Hipstamatic.
Hipstamatic is an app that mimics the results of low-quality toy cameras of the past. Translation: it takes some really groovy retro photos (and costs only $1.99!).
Since one wee app doesn't justify an iPhone purchase, I've been looking for ways to get Hipstamatic-like results during post-processing on my Mac. GIMP was moderately successful once I got past the (steep) learning curve, but the process was more time consuming than I wanted and the results were good but not stellar. There are a few options for Lightroom but nothing entirely satisfying. Since I don't use Photoshop, I can't speak to the quality of the actions available for it.
I tried several Polaroid knock-offs with varying degrees of success. Often these come with limited choices and strong color casts that yielded sometimes-interesting / sometimes-awful results. My favorite of the clones was Poladroid which I found to be fun and easy to use. You simply drag a jpeg to the icon, wait, and a Polaroid emerges. Rather like the real experience I remember from my childhood (only with less shaking).
Here's a sample image I created with Poladroid:
The top contenders to mimic the Hipstamatic seem to be Toycamera AnalogColor and CameraBag.
Toycamera offers the most control with 7 processes, 2 lens options, and the ability to add flare and Polaroid framing. You can adjust 9 additional variables including blur, contrast, color, and noise. It's essentially a mini-Lightroom aimed at creating toy camera results. While you can achieve striking results, more is demanded of the user in terms of experimenting and choosing well.
Here are samples processed with Toycamera AnalogColor:
CameraBag is a simpler system. There are 10 filters, 3 black and white and 7 color. Other than cropping and adding borders, your primary means of control lies in how you choose to layer the filters atop one another. While this can yield great results, I often found myself coming close to the image I desired and wishing I could make small tweaks in contrast or color to achieve it. This program gets points for authenticity since it better mimics the "take what you get" nature of inexpensive cameras. However, I found it frustrating to come so close at times and be unable to get the exact image I wanted.
Here are samples processed with CameraBag:
My verdict: those experienced with post-processing (and the control freaks) will probably enjoy ToyCamera AnalogColor more. Those who want simplicity and the ability to achieve Hipstamatic-like results with only a few clicks will find CameraBag to be a good option.