This summer might be sub-titled The Sally Kellerman Film Festival.

The unorthodox blond singer-actress will be starring in three movies - "Someone to Love," "All's Fair" and "Boardwalk" - and currently is working on a new film, "Boris and Natasha."All this activity from an actress whose choice of movie roles in the 1970s rates slightly below horrendous.

Kellerman made a spectacular impression as nurse Hotlips Houlihan in the movie "M*A*S*H" back in 1970, and great things were predicted for her.

But after "M*A*S*H," Kellerman starred in "Last of the Red Hot Lovers,""Brewster McCloud," "Lost Horizon," "Slither" and other forgettable films. She turned to nightclub performing and singing, including a record album.

"I thought I could just take off on a singing career and that when I came back to Hollywood the movies would still be here waiting for me," Kellerman said at her Hollywood Hills home.

"Boy, was I surprised."

Sally who? was the reaction of more than one producer. The show had moved on and Kellerman was no longer in demand.

Personal problems and professional hitches stalled her film career until the current spate of activitity, which includes a television pilot for a situation comedy co-starring Frank Langella.

"I guess you could say I'm a late bloomer," said Kellerman. "The big difference is my husband, Jonathan (Krane). He's a producer and he believes in me. In fact, he produced `Boardwalk' and will produce `Boris and Natasha.'

"Jonathan has backed me up and helped create interest in me in the Hollywood community. It took me years to realize this is a business, not just a place for me to express my artistic endeavors."

Kellerman worked for producer-director Henry Jaglom in "Someone to Love," in which she plays a movie star.

"Working with Henry was weird and wild," Kellerman said. "We finished the picture two years ago. It was Orson Welles' last performance. I think Henry shoots his movie; then sits down and writes it.

"`Boardwalk' is a serious drama. In the old days I used to play bums and alcoholics, which probably shortened my life by five years because I used to take the characters home with me. When I played a monster, I'd be a monster.

"Now I realize the thing to do is give my best shot every time I go to bat without killing myself. But it's not easy because every role an actress plays demands that she becomes that character to one degree or another.

"My psychiatrist tells me I should be more relaxed and creative on the set and forget my roles when I come home at night. I'm working on it. At least when I play silly roles I stay happy and jolly."

If that's the case, Kellerman should be in a good mood filming "Boris and Natasha," based on the characters in the old Jay Ward-Bill Scott cartoon series "Rocky and His Friends" and later titled "The Bullwinkle Show."

"I had never seen the cartoon show on television, but when Jonathan decided he wanted me to play Natasha I spent two days in New York City looking at a couple of hundred segments of the show," said Kellerman. "He cast Dave Thomas of `Saturday Night Live' to play Boris.

"The cartoons made me laugh. Boris is the dumbest Russian spy in history, and Natasha is madly in love with him. She can't keep her hands off of Boris. She is convinced he is brilliant.

"She wants to make love to Boris, but all he can think about is spying. Our problem was making the characters believable and not too cartoonish.

"We're keeping all the elements that make them human, interesting and funny. The whole film is set in America as Boris and Natasha go about spying . . ."