Not many online videos have sequels, but the one below–featuring a passel of celebrities, including Tom Cruise, Will Smith, Borat, Leonardo DiCaprio, Julia Roberts, Justin Timberlake, Scarlett Johansson and Harrison Ford–is one and even has famed director Steven Spielberg at the helm.

It is a follow-up to a PSA I posted earlier this month called “Hollywood Declares Themselves,” encouraging young people to vote.

It is from the nonpartisan group Declare Yourself, which has also put out the “Muzzler”/Jessica Alba get-out-the-vote advertising and video.

Declare Yourself is partnering with Google, YouTube and MySpace to distribute the new video, which has been produced by DiCaprio’s Appian Way .

Declare Yourself claims that “since it first debuted on Oct. 1st, the PSA has been viewed over 5,000,000 times. According to all major voting registration sites, including Google, Rock the Vote, and Declare Yourself, over 300,000 new voters registered due to the video alone.”

Here is the new video and also the previous two under it:

Spielberg Directs!

Hollywood Declares Themselves

“Muzzler”/Jessica Alba

One of the more interesting developments of this election cycle has been the boom in viral online videos being used–from a plethora of political spoofs of the candidates to educational videos to people simply venting.

And those pushing citizens, especially young people, to register to vote have been using the boom in online video too.

Last week, BoomTown featured one effort by a passel of celebrities to snarkily get people to vote by telling them not to (but not really).

This week, actress Jessica Alba turns into a Home Shopping Network maniac by hawking “The Muzzler,” for those who don’t vote.

It’s a lot over the top–including featuring a pink muzzle on indestructible “Heroes” cheerleader Hayden Panettiere.

But it does get the point through like a sledge hammer that it is important to vote in the Nov. 4 election.

Alba has already posed for several shocking pictures for the group doing the video–Declare Yourself, a national nonpartisan group dedicated to getting young people to vote–including wearing a muzzle and being bound by electric tape.

So, whoever you plan to vote for, here is a list of deadlines to register to vote in the 50 states, with many being today and the rest of this week.

And, here’s the Muzzler video: