These are all iPhone photo editing apps, but many (if not all, I didn't check) are available on Android.
This is by far my go to App. You start off with a whole list of crops sizes, including the instagram square, and then can layer your edits. There are about 60 different edits (or filters), which you can see in a live preview as to how they will affect your picture. My favorite that I use on almost every picture is "Lights On" it really brightens a picture. The best part, with the little slider at the bottom you can decrease/increase the strength of every filter; this is a huge plus!
If you find a certain edit you really like, maybe the 'lights up', 'saturation' and 'warm it up', you can save it as a recipe and it can become it's own one click edit.
You can then easily export the picture straight to Instagram, Facebook, Twitter, your camera roll and so many more.
I also love that for the $1.99 you get it all, no tricky in-app purchases later on for more filters.
When you want to add fun borders and texts I have two apps I love.
Rhonna Designs ($1.99)
If you have seen those pictures on Instagram with cute quotes and arrows and fancy designs; there is a good chance it came from the Rhonna Designs App. This App has a lot of prewritten quotes and also a lot of different fun fonts that you can write your own quote.
You can resize the words, symbols and text and can change the color. There are in-app purchases with this one, but there are frequent updates with more designs for free and it seems to continue to grow with more possibilities regularly.
A Beautiful Mess ($.99)
This is similar to Rhonna but more simplified with less options. The doodles and texts available seem to be more fun and whimsy. There are about 24 different font options and I love that they are all very different from each other and would fit a wide variety of picture styles. I feel like the selection is even great than in Rhonna's when it comes to text variety.
You can add multiple doodles or text and then can double tap on whatever doodle or text you want and can change or delete it. The Rhonna App seems to have a lot more options, but this app is more straightforward to use, but I love them both.
For this one I had a hard time picking my number one, as I think I use both equally, but might us Pic Stitch just a bit more; as long as both are still free, which InstagCollage is for a limited time, then either is great.
Pic Stitch (FREE)
From 1 to 16 picture collages, this has about 80 different collage layouts all free, with about 200 more you could purchase. But each layout is is actually adjustable in the resize option, so there really isn't much need to purchase additional layouts. All of the layouts are a square or rectangle crop.
This is much more than just a collage app though; when you click on each picture there are options for filters, ability to enhance, stickers, orientation, crop, adjustments, text, red eye, even healing blemishes and a cool focus where you can select what part is in focus, giving a slight blur to the rest of the picture.
I often forget there are these options though and usually just use this app for the collage itself.
InstaCollage (FREE for a LIMITED TIME!)
If you are looking for different shapes in your collage then this is the App for you. Triangles, circles, and just random shapes are some of the pictures options within these collages. There are over 100 different frames, including holiday, themes, multi color and various designs.
Each of these frames is adjustable to whatever color you like. You can also adjust the background and line color. You can slightly resize the size of each picture area and give it a rounded corner but you cannot totally change the size of each frame.
You can also edit each individual picture with extremely similar settings/filters/ etc. as PicStitch.
Have you seen those collages on Instagram that are actually little videos too? With 36 different collage layouts, you can post multiple videos in one "picture".
Have you seen those short videos on instgram flipping through pictures? That can be done with Flipagram. You can create a short video which flips through your pictures from your phone set to music. The more pictures you select the faster it will flip through. After you select the pictures you can change the order, crop the picture or even duplicate it. You can even pick pictures from your instragram feed.
Then you can either choose your own music, or choose a short music clip from a huge library of songs, everything from Disney, to classic, to country, dance and pretty much any style you could think of; they just ask that you copy a certain hash tag with the name of the artist and song when doing that.
Those are my favorite apps. This is by no mean a comprehensive list, just some that I have tried and used and I have kept, as I have tried many which I ended up deleting.
What Phone Apps do you use to edit pictures?