No federal laws have been passed that would protect journalists from releasing sources, notes, etc. However, in Feb. 2005, Senator Dodd introduced the Free Speech Protection Act of 2005.

Free Speech Protection Act of 2005; S369

From the Reporter‘s Committee for Freedom of the Press:
"The bill would provide an absolute privilege from disclosing sources whether they are promised confidentiality or not."

The government is prohibited from compelling any covered person from disclosing the source of information or any news or information that the person received (including notes, photographs, tapes, etc.).

The term covered person, in the context of this bill, means a person who "engages in the gathering of news or information and has the intent, at the beginning of the process… to disseminate the news or information to the public."

The term news media is any newspaper, magazine, journal or periodical, radio, television, wire services/press associations/news agencies, as well as any printed/electronic means of disseminating news to the public.
(This bill broadly defines who would be considered a journalist.)

However, the government may compel disclosure of information if: (1) the information is relevant to a case before any branch of the government that has power to subpoena; (2) the information cannot be obtained by alternative methods; and (3) there is an overriding and compelling public interest in the information.

Other pending legislation includes the Free Flow Information Act of 2005, which was proposed in the House and Senate

HR 581
S 340

The main difference between these bills and the Free Speech Protection Act is the definition of a covered person. In these bills, a covered person is one who publishes a newspaper, book, of magazine; operates a broadcast station, cable system, etc.; operates a news agency or wire service; a parent, subsidiary, or affiliate of such an entity; or an employee, contractor, or other person who gathers, edits, photographs, records, prepares, or disseminates news or information for such an entity.
This information directly from S 340

Therefore, many freelancers would not be covered unless they are under a contract with an entity.