By Steve Ryfle Aren't fame, fortune and the knowledge that you're at the top of your profession enough to satisfy the celebrity appetite?

No way. For decades, some of the most famous actors, musicians and other celebs have been branching out, not content to simply rest on their laurels or follow tradition.

Some stayed within their own profession and simply beefed up their resumes, like when Marlon Brando and Steve McQueen went behind the camera to become directors and producers. Others tried something completely new, such as when Elvis, Mick Jagger and David Bowie ventured out of the recording studio and into the movie studio.

Those guys did it 30 years ago, and today's celebrities are still doing it. They've been called "multi-platform artists," but really they're just famous people with unbridled energy and a tendency to get bored with routine.

Mogul Mania: Perhaps the most obvious way for a big star to branch out is to seize the means of production -- literally. Mel Gibson did it, forming ICON Productions more than a decade ago and establishing himself as a full-fledged producer and director, winning an Oscar for helming "Braveheart," making film history with "The Passion of the Christ" and bringing us the sitcom "Complete Savages." Tom Cruise and producer Paula Wagner formed Cruise/Wagner Productions in 1993, and the company is now one of the top production companies in Hollywood, churning out big-budget vehicles for Cruise and other stars. And don't forget Danny DeVito, whose Jersey Films has produced more than 20 movies, including "Erin Brockovitch" and "Pulp Fiction."

Un-Rapped: The Hip-Hop/Hollywood connection is nothing new, and rappers own a bigger piece of the movie game than ever. Ice Cube is probably the biggest success story, having parlayed his breakthrough in "Boyz N the Hood" into a huge career as actor, director, producer and screenwriter. Master P is now a one-man movie factory, producing, directing and writing a string of mostly straight-to-video flicks.

Other hip-hop artists have made lateral moves, becoming music moguls by forming their own labels. Sean "P. Diddy" Combs has his Bad Boy Records (and he also owns a clothing line), Eminem has Shady Records, and so on (nothing new here -- the Beatles, Led Zeppelin and Elton John, among others, all had their own labels back in the day).

Write Stuff: Some celebs choose to express themselves on the printed page. You know the story about Madonna's 1992 tome, "Sex" -- it was the biggest-selling coffee-table book in history, and the most controversial. These days, Madonna writes books for kids, with titles like "Mr. Peabody's Apples." Others have done the same, like singer Billy Joel, who just published "Goodnight, My Angel: A Lullaby" for pre-schoolers. Meanwhile, there are the serious literary types, like actor Ethan Hawke, whose novels have received good notices, as have the novels and plays of Steve Martin.

For a Good Cause: Liz Taylor is famous for fighting AIDS, and these days, dozens of stars have their own charitable endeavors and organizations. Paul Newman's mighty philanthropy extends from the millions of dollars generated for charity each year by his food products line to his Hole in the Wall Gang camps for children with life-threatening ailments; Gary Sinise co-founded Operation Iraqi Children; Michael Douglas hosts an annual charity golf tournament; Robert Redford, Elton John, Ted Danson -- the list of celebs spearheading organizations and/or raising money for their favorite cause is endless.

Power Players: For some celebrities, the politics of Hollywood are a stepping stone to the real thing. Arnold Schwarzenegger is just the latest to put stardom on the back burner for another kind of mass exposure. Clint Eastwood was Mayor of Carmel, Calif., the late Sonny Bono was a Congressman, and then there's Jesse Ventura. With fame bringing in cash contributions and friendly coverage from the celeb-driven media, the power of public office can be hard to resist.

How do they do it? For some, it's the desire to create new things in new genres, and to not be pigeonholed as an artist. And to some it's the freedom that comes with power. As Danny DeVito recently told Movie Poop Shoot: "The life of a producer! You go on the set, say hello to everybody, look at the costumes, shake a few hands, have a pastrami sandwich and there you go!"