You can submit a tip to the FBI tips website tips.FBI.Gov. You can submit your tip anonymously or you can include you name and contact number so FBI agents can contact you for more information if needed. You can also report a Ponzi scheme to the FBI by phone at 1-800-225-5324 or call the closest FBI office.
List of scam coins
USI-Tech - a classic Ponzi - possibly the world's largest in history
Kriptacoin scam taken down
Good site for staying safe and avoiding scams.
You want to avoid any cryptocurrencies that are offering regular returns and recruiting bonuses. These are almost always a sign you are dealing with a Ponzi scheme instead of a legitimate cryptocurrency. The money comes from new people joining.
Scam of the Month