Do I need to register with the CFTC or the SEC in order to sell my trading advice? Do I need some kind of license to start a trading strategy?

If you are an American citizen, the short answer is: No, you do not need to register with any government agency, or pass any kind of test, or have a license in order to publish trading advice.

However, you must be aware of certain restrictions. The most important restriction is this. You cannot provide individualized advice to clients. That is, you cannot offer different advice to different clients based on their individual  financial situations.

Here's an example.

Allowed: "Attention all subscribers to my trading system: Buy IBM because I believe it is going up!"

Not allowed: "Dear John Doe: based on our conversation earlier today, in which you told me you were nearing retirement, I think you should buy IBM, because it will appreciate in value!"

You must simply restrict your activity to publishing non-personalized advice which your clients can choose to act upon or not. (Note that using Collective2 to disseminate your trading advice via a Web site and email is considered publishing.) Remember that our right to publish and say what we like is protected by the First Amendment, a right that our citizens fight for, to this day. No small matter, that.

If you are not an American citizen, then I have no idea what kind of constraints your government places upon you. Please check with a local attorney.