The following are about 100 openly accessible REST APIs that you can browse as a way to look at patterns and examples. Most of these REST API links are available from programmableweb.com. I initially started gathering a list of the APIs in Programmableweb’s “Most Popular” category, but then I just started adding links as I ran across interesting APIs.
Programmableweb.com: A directory of API doc sites on the open web
For a directory of API documentation sites on the open web, see the Programmableweb.com. You can browse more than 13,000 web APIs.
Note that Programmableweb only lists web APIs, meaning APIs that you can access on the web. They don’t list the countless internal, firewalled-off APIs that many companies provide at a cost to paying customers. There are many more thousands of private APIs out there that most of us will never know about.
Look at about 5 different APIs (choose any of those listed on the page). Look for one thing that the APIs have in common.