Decide to build an API dashboard, but have no API

I've decided to create API dashboards for public use and also to strengthen my portfolio. I'm quite flexible regarding the topic, as long as it benefits people. I'm considering popular subjects such as salary trends over time, flu statistics, or news sentiment analysis.

​

However I have trouble in finding good data sources. Can anyone recommend any open or affordable API data sources?

analysis api benefits build dashboard dashboards datascience people popular portfolio public salary sentiment sentiment analysis statistics trends