By Stephanie DuBois What do Madonna, Jennifer Lopez, David Letterman, Ashton Kutcher, Robert De Niro and Pamela Anderson have in common? They all moonlight.Perhaps harkening back to the age-old advice that you shouldn't keep all your eggs in one basket, more and more celebrities are diversifying into areas outside their entertainment circle. Some are obviously moonlighting for economic reasons ? subsidiary ventures can provide excellent tax write-offs. Still others are branching out for the pure joy of utilizing a different set of creative juices. Whatever the reason, many celebs take their non-acting gigs -- whether it's owning nightclubs or restaurants or racing cars or designing clothing lines and signature perfumes or authoring books -- very, VERY seriously. Gone are the days of name only celebrity figureheads.

When Miss J to the L-O first launched her clothing line, she made it clear she would be involved in all aspects of the venture, from design to marketing. To ensure the clothing reflected the true Jenny From the Block, J.Lo reportedly personally worked and reworked each item till she was completely happy with the product. Though how she found the time to do that between her music, movies and men is anyone's guess.

Rapper Sean "P. Diddy" Combs has proven he's more than just Puff with his popular Sean John collection. J.Lo's one time paramour copied his own singular sense of style and his hot selling men's sportswear line reportedly had $150 million in sales last year, in addition to receiving several nominations from the Council of Fashion Designers of America.

Other rappers such as Nelly, Eminem and Jay-Z jumped into the clothing fray -- or frenzy as it's starting to become -- with Jay-Z's line, Rocawear leading the pack. The line is expected to rack up $300 million in sales this year and that doesn't include the bling bling being generated by Jay-Z's $100 sneakers, the S. Carter (the rapper's real name) put out by Reebok.

Now it seems like stars are coming out of the woodwork to compete with the likes of Versace, Hilfiger and Ralph Lauren. Pamela Anderson is expected to debut "The Pamela Collection" next February in Las Vegas. She says she has creative control and will co-design the line skedded to hit stores in Fall 2004. Destiny's Child diva, Beyonce, also has plans to launch not one, but two clothing collections next year with her mom and design partner, Tina Knowles, who's also Beyonce?s stylist.

While these celebs are doing their all for the outer you, others are doing their all for the inner you. The ever growing list of celebrity restaurateurs includes Robert DeNiro, who owns or co-owns the trendy Nobu and Ago restaurants in L.A., as well as the popular Tribeca Grill in New York. That gang from "That 70s Show," Ashton Kutcher, Wilmer Valderrama and Danny Masterson, are co-owners of L.A's Italian eatery, Dolce. And, of course, there's Madre's, the Cuban restaurant in Pasadena owned by J.Lo, who just can't seem to help having a finger in every pie.

Then there are those celebs utilizing other creative juices to make inroads in the literary world. Madonna is the latest to break into the children's book market following in the successful footsteps of Jamie Lee Curtis, Will Smith and John Lithgow. Madonna's "English Roses," which was published in 100 countries and 30 different languages, sold more than 50,000 copies in less than two weeks. Next year we can expect more literary offerings for the kiddies from Billy Crystal and "Tonight Show" host Jay Leno.

Leno rival David Letterman, is among the celebs who like to moonlight in the fast lane. Letterman is a minority owner of an Indy racing team owned by Bobby Rahal. Other celebs caught up in the thrall, er thrill, of auto racing include, Pink Floyd drummer Nick Mason and Jason Priestley, who almost lost his life last year when he crashed head-on into a wall and fractured his spine.

However, Paul Newman has reportedly spent more on racing than any other actor ? approximately $100 million. Newman began racing competitively in 1972 and has co-owned the Newman-Haas team in CART since 1983. He has said, "The only sport I ever found any grace in was automobile racing." That may be, but he turned his Newman's Own line of food products -- launched in 1987 with two thousand bottles of vinaigrette salad dressing made from his own recipe ? into a seemingly bottomless gold mine for Newman's various charitable endeavors. And, of course, he's not a bad actor either!