What Are the 17 United States Intelligence Agencies?

The U.S. intelligence community has been prominent in the news in the past few weeks. This will probably continue in coming weeks and months as the Senate Intelligence Committee launches an investigation of allegations of ties between Russia and 2016 political campaigns. This investigation will be part of a broad review of the intelligence community’s report on Russian hacking.
National Public Radio national security correspondent Mary Louise Kelly recently explained the intelligence agencies, how they relate to each other, and how they may be involved in the investigation into Russian involvement. The interview transcript and audio can be found here.

http://www.npr.org/2017/01/10/509086405/heads-of-4-u-s-spy-agencies-to-appear-before-senate-panel-on-russia

The Washington Post article describing the upcoming Senate investigation can be found here.
https://www.washingtonpost.com/news/powerpost/wp/2017/01/13/democrats-accuse-fbi-director-of-stonewalling-on-trump-russia-ties-as-more-call-for-him-to-step-down/?utm_term=.0f31f186a9a5
 
Here is a list of all the federal agencies with intelligence gathering authority:

1. Coast Guard Intelligence
2. Department of Energy
3. Treasury Department
4. State Department
5. Army Intelligence and Security Command
6. Office of Naval Intelligence
7. Twenty-Fifth Air Force
8. Marine Corps Intelligence Activity
9. Defense Intelligence Agency
10. National Geospatial Intelligence Agency
11. National Reconnaissance Office
12. National Security Agency
13. Drug Enforcement Administration
14. Department of Homeland Security
15. Federal Bureau of Investigation
16. Central Intelligence Agency

AND OVERSEEING THEM ALL:
          The Office of the Director of National Intelligence