Either you are a developer, or an coder afficionado, you can save a lot of time simply individuating the right API that expose a set of information that can be extremely useful to you. As usually on the www world, they can be pretty hard to find and discover and this is why i'm writing this two lines since i selected some of the best and interesting API that may result interesting to you.
1 - Twilio
Twilio is a telecommunications company which freely provides API for voice and text. You can easily send or receive phone calls, SMS, MMS and so on, so using this API you can embed in your app source code some features to deal with telecommunications.
2 - FullContact.com
Fullcontact provides a set of API for building up and gather information on a specific individual, simply provding a bit of information. Is a sort of function who returns the complete web identity of people. Nice to try, usefull for salers and marketers or for services where the identity needs to be verified or checked.
3 - BreweryDB
Yes, you read well, there are also API about the most important thing for a developer, which beer choose at the end of the workday. You can find all of them here, and if you are brave enough you can also add on your app source code.
4 - RestCountries
You are teaching capitals of remote place to your son? Automate this stuff with these API. They returns flags, demography information, cities and so on on each country you are looking for.
5 - API NASA
Do you want unique and stunning space wallpapers in your pc but you no longer want the OS default ones? Do you want to see extremely high resolution photos from Mars?
NASA exposes its own API and their are amazing.
6 - Cat Facts
Ok, you set up as wallpaper of your little boy's pc a 4K photo of mars landscape. What for your little princess's pc? Cat facts provides pictures and nice facts about cats. Both happy.
7 - Moneypot
Simple API to gambling a bit with cryptocurrencies
Any menaningful API missing here? Suggest them in comments !