Enacted legislation:

CAN-SPAM Act of 2003 (Pub. L. 108-187, S. 877)
The Controlling the Assault of Non-Solicited Pornography and Marketing Act requires unsolicited commercial e-mail messages to be labeled (though not by a standard method) and to include opt-out instructions and the sender's physical address. It prohibits the use of deceptive subject lines and false headers in such messages. The FTC is authorized (but not required) to establish a "do-not-email" registry. State laws that require labels on unsolicited commercial e-mail or prohibit such messages entirely are pre-empted, although provisions merely addressing falsity and deception would remain in place. The CAN-SPAM Act took effect on January 1, 2004.
The CAN-SPAM Act of 2003 was introduced by Senators Conrad R. Burns (R-MT) and Ron Wyden (D-OR) in April 2003, with minor changes from the previous year's version, S. 630 (2002). Two other bills (S. 1231 and S. 1293) were subsequently merged into it. The final version was approved by the Senate in November 2003 and by the House of Representatives in December 2003, and was signed into law by President Bush on December 16, 2003.

Not yet enacted bills:
Anti-Phishing Act of 2004 (S. 2636)
The Anti-Phishing Act of 2004 was introduced on July 9, 2004, by Sen. Patrick Leahy (D-VT); it would prohibit, among other activities, sending e-mail that directs recipients to a website that falsely purports to belong to a legitimate online business and solicits recipients to provide personal information.
Anti-Spam Act of 2003 (H.R. 2515)
The Anti-Spam Act of 2003 was introduced on June 18, 2003, by Rep. Heather Wilson (R-NM); co-sponsors include Rep. Rick Boucher (D-VA) and Rep. Ed Markey (D-MA). The bill would require all commercial e-mail messages to be identified as such (but not with a standard label, except for sexually explicit messages), and to include the sender's physical street address and an opt-out mechanism; messages relating to a specific transaction and consented to by the recipient would be exempt from those requirements. The bill would prohibit commercial e-mail messages with false or misleading message headers or misleading subject lines, and it would be illegal to send commercial e-mail messages to addresses generated by an automated dictionary attack. State laws that restrict the sending of commercial e-mail, regulate opt-out procedures, or require subject-line labels would be pre-empted; laws that merely regulate falsification of message headers would remain in effect.
Ban on Deceptive Unsolicited Bulk Electronic Mail Act of 2003 (S. 1052)
The Ban on Deceptive Unsolicited Bulk Electronic Mail Act of 2003 was introduced by Sen. Bill Nelson (D-FL) in May 2003. It would prohibit the inclusion of false information in message headers in unsolicited bulk commercial e-mail. It also would require senders of unsolicited bulk commercial e-mail to include opt-out instructions and honor opt-out requests, and would prohibit them from harvesting e-mail addresses of potential recipients from web pages and other sources. Violations of the law could be prosecuted under RICO.
Computer Owners' Bill of Rights (S. 563)
The Computer Owners' Bill of Rights, introduced by Sen. Mark Dayton (D-MN) in March 2003, would require the Federal Trade Commission to establish a "do-not-email" registry of addresses of persons and entities who do not wish to receive unsolicited commercial e-mail messages. The FTC would be empowered to impose civil penalties upon those who send unsolicited commercial e-mail to addresses listed on the registry.
Criminal Spam Act of 2003 (S. 1293)
The Criminal Spam Act of 2003 was introduced on June 19, 2003, by Sen. Orrin Hatch (R-UT); among the co-sponsors are several senators who have sponsored other bills listed here. The bill would prohibit unauthorized or deceptive use of a third party's computer for relaying bulk commercial e-mail messages. It also prohibits the use of false header information in bulk commercial messages, and regulates the use of multiple e-mail accounts or domain names for purposes of sending such messages. The law would apply only to quantities of more than 100 messages within 24 hours, or 1000 within 30 days, or 10,000 within one year.
REDUCE Spam Act of 2003 (H.R. 1933)
The Restrict and Eliminate the Delivery of Unsolicited Commercial Electronic Mail or Spam Act of 2003 was introduced by Rep. Zoe Lofgren (D-CA) in May 2003. Under the REDUCE Spam Act, unsolicited bulk commercial e-mail messages would be required to include a valid reply address and opt-out instructions, and a label ("ADV:" or "ADV:ADLT", or other recognized standard identification). These requirements would apply to messages sent in the same or similar form to 1,000 or more e-mail addresses within a two-day period. In addition, false or misleading headers and deceptive subject lines would be prohibited in all unsolicited commercial e-mail messages, whether or not sent in bulk.
Reduction in Distribution of Spam Act of 2003 (H.R. 2214)
The Reduction in Distribution of Spam Act of 2003 was introduced in May 2003 by Rep. Richard Burr, R-NC; cosponsors include Energy and Commerce Committee chairman Rep. Billy Tauzin, R-LA, and Judiciary Committee chairman Rep. James Sensenbrenner, R-WI. The bill would require all commercial e-mail messages to be identified as such (but not with a standard label, except for unsolicited sexually explicit messages), and to include the sender's physical address and an opt-out mechanism. It would prohibit the use of false or misleading headers in commercial messages. State laws that prohibit unsolicited commercial e-mail, regulate opt-out procedures, or require subject-line labels would be pre-empted; laws that merely regulate falsification of message headers would remain in effect.
Stop Pornography and Abusive Marketing Act (S. 1231)
Sen. Charles Schumer (D-NY) introduced the Stop Pornography and Abusive Marketing Act, or "SPAM Act," in June 2003. The bill would establish a national "no-spam" registry, and make it unlawful to send unsolicited commercial messages to addresses on that list. The list would be administered by the FTC, using fees paid by marketers for access to the list. The FTC would be empowered to prohibit explicit commercial messages to minors even if they were not on the list. All unsolicited commercial messages would be required to use a label ("ADV:") at the beginning of the subject line, except those sent in compliance with an FTC-approved self-regulatory program. It would be illegal to send any commercial e-mail in violation of an Internet service provider's policies, or with a false or misleading subject line or message header, or to harvested addresses; all commercial messages would be required to include the sender's physical address.
Wireless Telephone Spam Protection Act (H.R. 122)
H.R. 122, introduced by Rep Rush D. Holt (D-NJ) in January 2003, would prohibit the use of wireless messaging systems to send unsolicited advertisements.