I was having fun with Instagram a couple months ago to quickly present photos in fun or more pleasing ways. I discovered the free app from Aviary recently, though, and I haven't done anything with Instagram since.
Most of the features I use are all free, but there are some in-app purchases for more effect packs. I bought the Grunge pack for $0.99. (I still love taking pictures that I imagine will be the cover of my hit recording.)
Aviary uses the engine from the original Aviary image editing tools (which unfortunately are no longer available). I have always been impressed with their free online applications. The app version is a very slimmed down editing tool, but it has become my favorite tool for editing photos on the iPad.
Aviary allows me to share right to Twitter and Facebook.
You also get extra tools to add more control than Instagram allows (at least from the last time I looked at Instagram). There are Paint, Text and other common editing tools. I like the stickers if, for nothing else, I want to add some funny speech bubbles. That alone makes it a good app to use in the classroom to edit pictures for comics. The meme tool is a lot of fun too.
There are a few tools that automatically adjust color balance for different lighting situations, though I can't speak much to their effectiveness. I usually just tweak the brightness and contrast, so I'm glad those tools are available.
I most appreciate the filters for a final touch to pictures. Aviary calls them Effects and in the time since I originally posted this they improved them quite a bit. The app allows you to add the effects and frames separately now, so with a little work you can really make some attractive final products.
But in the end, it's free. There's really no good reason not to add it to your device for the additional options.
Here are some examples, the first two being recent additions using the latest version of the app:
Quick fun while we helped some friends move to a new house.
One of the basic Effects.
This is my outdoor "office".
We hit 100 degrees yesterday in Michigan, but this was taken quite early in the day.