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

Here’s an interesting online video, in which a passel of celebrities urge young people to vote.

It begins with them urging youth not to vote, in that hipster, sarcastic, of-course-we-really-mean-you-should-vote-you-dope tone.

The nonpartisan PSA–well, honestly, it does lean decidedly liberal–has been produced by actor Leonardo DiCaprio’s Appian Way and includes DiCaprio, Jennifer Aniston, Dustin Hoffman, Eva Longoria, Forest Whitaker, Ellen DeGeneres, among others.

Also, inexplicably, comic Sarah Silverman taking off her bra to prompt young people into civic action.

And if that’s not reason enough to prompt you to register to vote–deadlines are looming for the upcoming election–and get to the voting booths on Nov. 4, BoomTown does not know what is.

Here’s the video: