Offers of help in rebuilding the Filene Center, destroyed by fire last Sunday night, have begun pouring in to the Wolf Trap Foundation, from organizations that range from national corporations to small, local business and performing arts groups. The largest concrete sum registered so far is $50,000 from the RKO General Corp., but it may be surpassed by an open-ended offer from Neiman-Marcus: 20 percent of net sales in its Washington store during the three-day period from Thursday, April 15, through Saturday, April 17.

There have been no reliable estimates on the cost of rebuilding the center, but Catherine Filene Shouse has speculated that it may run between $8 million and $12 million.

Many offers of help, like the Neiman-Marcus one, have an uncertain bottom line. The Summer Opera Theatre Company has offered the total ticket sales for its gala opening night performance of "Madame But terfly" on July 14 at the Hartke Theatre, and if all tickets are sold that should amount to more than $20,000.

Other performing arts organizations planning benefits range from the still new and struggling Washington Gay Men's Chorus (which will give proceeds of a performance at the Warner Theatre near the end of April) to a group of four performing arts organizations in Richmond that will give a joint gala, co-chaired by Shouse, Gov. Charles Robb and his wife, Lynda Bird Robb. Performing groups will be Richmond's Symphony Chorus, Ballet, Camerata and a local opera group.

Some gifts will be raffled off, such as a four-day trip to Vienna, Austria, offered by the V.I.P. travel agency in Vienna, Va. And for many, the final planning is not yet firm. In Laurel, Md., for example, the Freestate Raceway has offered one day's gate receipts, but the offer may escalate into a more ambitious Wolf Trap Day at the Races that would involve other sources of income.

In Washington, the Tommy Dorsey Orchestra is cooperating with the Assembly of Government Employees to organize a big-band benefit ball, probably in early May, but details are still uncertain. They are "trying to get the Washington Hilton involved and to make it a really spectacular affair," said a spokesman.

Details will probably be settled today on plans for a week-long media-blitz fund-raiser in which the Washington Area Broadcasters Association is trying to get all local radio and television stations to participate. About 30 Washington stations are expected to be represented at a meeting this morning called by WABA chairman Jerry R. Lyman and scheduled to be held in the downtown home of Catherine Shouse. "I'm calling it 'Washington for Wolf Trap,' " said Lyman, "and my hope is that, with 30 stations cooperating, we can raise $1 million in a week."

It was Lyman who, as vice president and general manager of WGMS, persuaded RKO General to contribute $50,000, half of which will probably be used for matching funds during the week-long WGMS radiothon for Wolf Trap, which begins Monday. The gift was approved in New York by Hubert DeLynn, vice chairman and chief operating officer of RKO General.

In Dallas, chairman Richard Marcus of Neiman-Marcus approved the open-ended gift pegged to three days' net sales in the Washington store. "We were thinking about what we could do for Wolf Trap," executive vice president Tom Alexander reported from Dallas. "Most of us have enjoyed a performance there at one time or another. And then this idea came through from our Washington store, and it got quick approval."

Dee Dee Bufe, manager of the Washington store, could not give a firm figure on how much money might be raised in the three days. "The potential is unlimited. If we had done it at this time last year, it would have been about $50,000, but if we could double that figure, we would love it. I certainly hope our offer will draw new people to the store, and it would probably be a good week anyway. A lot of people are planning to buy spring clothes and have delayed because of the weather, and many may plan to do their Mother's Day shopping a little early."

She said she was particularly glad to be able to help Wolf Trap for two reasons related to the store's image: "We want people to see us as part of the community, rather than a Texas store that just came in. And we like the broad base of people who go to Wolf Trap. People who sit on the lawn--not just the elite; not just the leaders of society."