Believe it -- the best things in life can be free. And to prove it is the third Inside/Out open house from noon to 7 p.m. today at the Kennedy Center.

"It's the only day of the year when the usual events are put on hold and our doors are thrown open to the public," says Tom Mader, executive director of Friends of the Kennedy Center, sponsor of the event. "For a lot of people, I think the idea of the Kennedy Center is daunting. We want them to feel comfortable here."

"We have an eclectic mix of groups, from theater to dance and magic, to mime, to rock to country to classical," says Mader. "On seven stages, including the outdoor ones, with 85 groups, there's going to be something different going on every moment."

For Washington-born classical soprano Chrisselene Petropoulos, who will perform at Inside/Out, the open house is an indication that her home town is coming into its own artistically. "If you want to create a cultural mecca, you've got to keep the artists here," she says. "To do that, you have to give them work."

In addition to Petropoulos, the talent lineup includes the rockapella group Betty, Sweet Honey in the Rock, Mary Chapin Carpenter, country legend Patsy Montana (one of the few non-Washingtonians performing), Everyday Theatre and Liz Lerman's Dance Exchange. Also performing will be the National Symphony Orchestra and the Washington Opera. The American Film Institute will show films throughout the day.

"This is our way of saying to area residents: This is your center and these are some of the best that the metropolitan area has to offer," says Mader. "Enjoy, and come again."

For more information, call 254-3600.