Play local media files or use streaming apps with no Chromecast support. The Google dongle will get your content up on the big screen.
10 Awesome Things You Didn't Know Your Google Chromecast Can Do
How to Set Up Google Chromecast: iPhone, iPad, and Android
You Otter Be Able To Stream That Audio: Open Hardware Eclipses Chromecast Audio
How to protect yourself from streaming hacks
20 Things You Didn't Know Your Google Chromecast Could Do
Chromecast Audio
20 Things You Didn't Know Your Google Chromecast Could Do
20 Things You Didn't Know Your Google Chromecast Could Do
20 Things You Didn't Know Your Google Chromecast Could Do
Google Chromecast - Streaming Media Player in 1080p GA00439-US - The Home Depot