Buy Season 1:
Buy Season 2:
I'm being a little more snarky than I need to be; on the whole, the show was well-done, and the opening episode pulled excellent numbers. I mention The 4400 here not because of their basic "press kit" web site, linked above; it's OK, but generally unimpressive. There are a few character profiles (with very little information in them, I should add), some downloads, and a discussion board with about 6500 entries -- OK numbers, but not great. What was, or rather could have been interesting, was a website shown briefly during the show, the4400scoop.com. In the show, this site appeared to be the creation of some people who were highly suspicious of the 4400's return, and it was being used as a collection and distribution point for alarmist information and theories about the returnees. However, the site doesn't actually exist, although Viacom did go to the trouble of registering the domain name, as a quick trip to a WHOIS facility will show you.
Developing this site could have been a nice promotional tool for the show: Build a bit of content for the characters featured in the show, themed to emphasize the mysterious and possibly threatening nature of the appearance of the returnees, and launch the site a month or two before the series' launch. Keep the site updated on a somewhat regular basis so that people have a reason to return, and move or copy the discussion boards from the main show site to the "scoop" site, so there's a place to debate and discuss the show's story as it unfolds. But it didn't happen; c'est la vie. Consider it a missed opportunity.