Few columns touch as many hearts as Ann Landers'. She can touch nerves, too, as on Sept. 8, when she ran a letter from Monsignor John Egan.

The Chicago priest, who is both nationally known and much-loved by his flock, told the Landers audience about Friends of VISTA, the Washington-based nonprofit advocacy group that promotes and protects the federal Volunteers In Service To America program. Egan urged former volunteers to write Friends of VISTA as a way of broadening the organization's base, and he supplied a Washington address: 1000 Wisconsin Ave. NW, 20007.

Write they have. More than 1,100 men and women responded in the following two weeks. The letters are worth a look because they coincide with congressional hearings on what kind of legislation is needed, if any, to promote national service. VISTA's name and lustrous record rarely come up, yet 90,000 citizens have given a year or two of their lives as volunteers in social programs ranging from inner-city food banks to rural health clinics.

VISTA -- created in the mid-1960s along with Head Start, Jobs Corps, Legal Services, Upward Bound and other successful durables -- has been called the domestic Peace Corps. The major difference in the two programs is that throughout the Reagan years Peace Corps has had one director and VISTA has had six. Loret Ruppe has fought creatively to strengthen Peace Corps while VISTA's directors, including Constance Horner, now onto weightier issues as the head of the Office of Personnel Management, worked to weaken their program. The six marched to orders from an administration that once sought to phase out VISTA and another time requested an immediate funding cut-off.

Friends of VISTA, whether serving as a bedside IV bottle to revive the program's assaulted body or as a bell-ringer to alert Congress to pending attacks, could also call itself the Grateful Friends of VISTA. Letters prompted by the Landers column run deep with personal testimonies of former volunteers staying close to the path that VISTA first set them on.

The assistant to the mayor of Detroit wrote: ''I was a VISTA volunteer from Aug. 16, 1965 to Aug. 16, 1966. I trained in Baltimore and was assigned to the United Planning Organization's neighborhood development center in Washington, D.C. My VISTA year (which began when I was 18 years old) was more valuable than any college class I ever took and laid the foundation for my entire career.''

A husband and wife wrote from Lansing, Mich., to recall their days in the late '60s: ''VISTA actually set the tone for our lives. We both became social workers and have spent our lives working with this country's poverty stricken and disadvantaged.''

From Portland, Maine: ''I am a former VISTA volunteer from 'the good old days' (pre-Nixon 1967-69) and would like to keep this valuable program alive any way I can."

Aside from supporting a program that is half its mid-1970s size, the letters help refute the fashionable myth that the 1960s were a time of self-indulgence in useless love-bead causes. The 1960s contingent of VISTA alumni were not misfits then, and, from the evidence of these letters, are not now. Lisa Woll, director of Friends of VISTA, reports that former volunteers -- ranging from a U.S. district court judge in Minneapolis to a chief of police in Nebraska -- are a pool of talent that would probably have never been formed without the VISTA experience.

That the program has been treated shabbily these past seven years is part of the general onslaught on the poor by the Reagan administration. It rarely misses a chance to pounce on the weak, preferably when no one is looking. VISTA has survived because someone has been looking, from allies in Congress to Ann Landers