At least a half-dozen letters from today's mail ought to be shared with readers, but there's space for just one.

It's from a man who finally retired and, having time on his hands, went to the racetrack at Laurel for the first time in his 68 years of residency here.

To his astonishment, he won $22 - and promptly sent me a check in that amount for Children's Hospital. Don't ask me how a rank amateur managed to win when our resident expert, Clem Florio, who is one of the best handicappers in the country, lost his entire mythical bankroll. Clem would probably want to know the answer to that one himself.

We begin today's report on contributions from groups with the $18.18 sent in by "some of the engineers and their helper at 2029 K Street NW." No holiday card exchange among employees of Banner Glass (Rockville) brought in $21. Shortly before Christmas, the Senior Choir of the Wheaton Parish of St. Mary Magdalene Episcopal Church sang for the Silver Spring Lions Club. The club later sent the choir a $25 honorarium, and the choir sent it to me for Children's Hospital. Another $25 arrived from the Boston House (1711 Massachusetts Ave. NW) Tenants Association, and employees of the Legg Mason brokerage office in Gaithersburg also took up a kitty of $25.

The Foxhall Ladies Bowling League of Wheaton rolled $26 down my alley. Employees of the Systems Analysis & Programming Branch of (are you ready?) "ADPSA, MDW-DMISS" used to exchange gag gifts at Christmas, but this year they scrubbed the gift exchange and sent me $28. Don't ask me what ADPSA, MDW-DMISS stands for. The only initials I recognize in the group are MDW as in military District of Washingon.

No card exchange among employees of Rockville Glass Service brought in $29. No gift exchange among employees of High's Store 848A (Beltsville) was good for $34 worth of medical help for a needy child.

From Mount Rainier came a $43 check from "our Monday Area Church Bowling League." The Field Inspections Division of the Metropolitan Police Department refrained from exchanging $55 worth of in-house holiday cards. Employees of the American Podiatry Association didn't foot the bill (forgive me; I can't resist corny puns) for sending each other $95 worth of greeting cards.

No card exchange among the men and women at Pohanka Oldsmobile in Matlow Heights took $152 off the sticker price of the deficit at Children's Hospital. The Office of Publications at the Department of Commerce raised $161. The staff at the Heritage Foundation (it's a public policy research foundation) chipped in $175.

When the Office of Budget Department of Housing and Urban Development received a group award recently, each employee was given the option of taking his share of the cash or signing it over to Children's Hospital. The majority elected to support the hospital with the built-in deficit, which netted $212.66. A tip of the hat to you, budgeteers.

Employees of the Statistics Division of the Internal Revenue Service made $219.37 worth of tax-deductible contributions to the children. The men and women at the Leon Office Machines Co. rounded up a few more checks to add to their previously recorded gift - this time a mere $222.35 worth.

Officers and employees of Delta Electronics in Springfield, Va., didn't send holiday cards to each other, but they did send me the $223 they saved thereby. For the sixth straight year, members of the Science and Technology Division of the Institute for Defense Analyses adorned their Christmas tree with gifts to Children's Hospital. This year their checks added up to $245. Employees of the National Coal Association didn't send each other $275 worth of holiday cards. Remember coal? Of course you do. It's that black stuff we rediscovered when the oil suddenly ran short.

No card exchange among employees of the National Cable Television Association brought in a half-pound of checks that added up to $300. The Andrews Federal Credit Union at Andrews AFB sent me $321 in memory of a staff member who passed away in April. And top honors for the day went to the men and women at Steven-Windsor who took a $630 whack at the buil-in deficit.

As I tally it on my cordless abacus, that's $3,560.56 from 24 groups and $787.45 from 33 oridnary mortals plus one phenom who beat the horses, to bring today's receipts tp $4,348.01. Having started the day with $104.456.79, we now have $108,804.80 in the shoebox.