Here are a few of the apps I use every day for retouching, color correcting, watermarking, and titles. These are great for editing on the go and for easy, quick posting to all your social media sites.
Most photographers will be familiar with this program. Photoshop Express comes from the leader in photo and video editing software: Adobe. This is a go-to app when you need to adjust color, temperature, exposure, tint, ect. This versatile app gets the job done and is as simple to use as it gets. edit and crop your photos for Instagram and really pull out that rich color with this app!
Another app that has some great features for editing on the go is Pixlr Express. While slightly less user friendly than PS Express, Pixlr Express is a bit more in depth when it comes to tools. Now, this can be both good and bad, so try both apps out to really see what features you will most use from each. 95% of the time, I turned to PS Express as it is simplified and more straight forward than Pixlr Express, but there are times when I need that one filter or some funky thing PS doesn't have. This is the app I turn to to fill the gap.
IWatermark is the app I use to add watermarks to the photos I post online. If you are looking for a watermark program to protect your photos, this is the best I have found. I have tried many different apps for this task, but nearly all of them cut your picture quality in half. As a photographer, that is the last thing you want. IWatermark maintains photo quality and integrity while also being extremely easy to use. Once you've made your watermark, just load an image, select your mark, place it where you want and save or upload directly to your social media sites. It's that simple!
For simple, clean and high quality titles on the go, I use TitleFX. Again, quality is key when working with photographs. You don't want to slap a grainy, fuzzy title on your photo and call it a day. TitleFX may not offer a ton of fonts to choose from, but what fonts they do offer are among the cleanest and most commonly used. Many apps will tout "2000 fonts," but who uses DingBat or half of the crazy fonts out there? TitleFX gives me the good ones on the go and lets me get the job done right.