WB.com
Official USA Network site for the series.

IMDb
The IMDb listing for The 4400.

TV.com/The 4400
TV.com (formerly TV Tome) provides detailed information on the series, episode descriptions and air dates.

Solitary Phoenix/The 4400
A dedicated fan site with good backgrounders on the characters.

4400 TV Fan Site
A comprehensive French fan site.

The 4400 Forum.com
A dedicated bulletin board featuring discussions about The 4400, science fiction and UFO phenomena.

iwasabducted.com
Information on abduction, UFO sightings, and crop circle phenomena; probably to be taken with a grain of salt and provided here strictly for entertainment value

US Department of Homeland Security
Official website for the U.S. Department of Homeland Security