Dog days of August got you down? Itching for the fall theatre season to begin? Well, here are two items to bring joy to the heart of every New York theatregoer. Come September, it'll be time once again for the Broadway Flea Market (Sept. 27) and the "Broadway On Broadway" Concert in Times Square (Sept. 7).

More than 50,000 people are expected to attend the 6th annual "Broadway On Broadway" concert in Times Square, Sept. 7, noon. The 90 minute revue, featuring casts from current and upcoming shows (such as 1776 and Triumph Of Love), is presented by Continental Airlines and American Express.

According to spokesperson Alex Chambers (of Rubenstein & Associates) tentatively scheduled to sing at the free "Broadway On Broadway" concert are Capeman's Marc Anthony & Ruben Blades ("Time Is An Ocean"), marking the first time music from The Capeman would be heard outside a rehearsal hall. (Despite rumors that composer Paul Simon would perform, as of Aug. 14, concert spokesperson Adrian Bryan-Brown told Playbill On-Line Simon was not scheduled to appear.)

Also scheduled to appear at the concert are:
On The Town's ensemble ("New York, New York");
1776's (probably) Brent Spiner and ensemble;
Rent's ensemble ("Take Me As I Am");
Annie's Brittny Kissinger, Orphans and Sandy ("A Hard-Knock Life");
Chicago's James Naughton & Marilu Henner ("All I Care About Is Love");
Jekyll & Hyde's Linda Eder, Robert Cuccioli, Christiane Noll.
Cats' Laurie Beechman ("Memory");
Phantom Of The Opera's Tom O'Leary ("Music Of The Night");
The Life's Lillias White & Ladies ("It's My Body");
The King And I's Faith Prince & Kids ("Getting To Know You");
Smokey Joe's Cafe's ensemble ("I'm A Woman")
Titanic's ensemble (opening sequence)
Grease!'s Lucy Lawless.
Noise/Funk's Ann Duquesnay.
Funny Thing...Forum's David Alan Grier & Ernie Sabella.

* The 11th annual Flea Market, Sept. 27, will be held once more in Shubert Alley (West 45th St.), 10 AM-7:30 PM. The event mixes visits by Broadway stars with sales of such merchandise as posters, CDs, signed scripts, snacks baked by Broadway cast & postumes, Playbills and other memorabilia. Flea Market visitors can also come to the "Celebrity Table" and get autographs/have their pictures taken with Broadway, Off Broadway and soap-opera stars.

Specialty items will also be offered at the "Grand Auction," with bidding starting at 10 AM and taken until 3:30 PM. The silent auction officially begins at 4:30 PM. This year's goodies will include walk-ons in Rent, The Life, Titanic, The King And I, Miss Saigon, Beauty & The Beast, and several NY-based television shows.

Here's a tentative roster of celebrities expected for the Flea Market:
(11 AM-noon): David Alan Grier (Forum), Victoria Clark (Titanic), Marilyn Cooper (Grease!), Alma Cuervo (Titanic), Jessica Hecht (Ballyhoo), John Herrera (1776), Bebe Neuwirth (Chicago).
(noon-1 PM): Gibby Brand (Beauty & The Beast), Beth Fowler (Beauty & The Beast), David Garrison (Titanic), Cris Groenendaal (Forum), Marcia Lewis (Chicago).

Of course, all proceeds from the Flea Market & Auction will go to Broadway Cares/Equity Fights AIDS, which has, since October, 1987, raised and distributed $25 million in the fight against the disease.

Here are some highlight lots from the Grand Auction. Bids are accepted by phone from those unable to attend the event; call Carla Cherry at (212) 840-0770.

* Framed poster commemorating the 51st annual Tony Awards (this past June), signed by Rosie O'Donnell and all the presenters, including Hal Holbrook, Raquel Welch, Whoopi Goldberg, Bernadette Peters, Marisa Tomei, Mandy Patinkin, Lauren Bacall and Julie Andrews.

* The sweater Betty Buckley wore in Carrie -- complete with a signed letter by Buckley verifying the garment's authenticity.

*  ten musical phrases, signed by such composers as Stephen Sondheim, Kander & Ebb, Flaherty & Ahrens and Strouse & Adams (separate lots).

*Framed, signed movie poster of Planet Of The Apes.

*A pair of opoening night tickets to Proposals,, The Scarlet Pimpernel, The Capeman, Ragtime.

* Authentic mimeographed program from A Chorus Line when it was at the Public Theatre -- signed by Donna McKechnie.

* Playbills signed by Tallulah Bankhead, Ruby Keeler, Lauren Bacall, Ingrid Bergman and Carol Channing.

* Walk-on on TV's "Friends," including air-fare and hotel.

* Memorabilia from Sunset Boulevard, including a script signed by Andrew Lloyd Webber, a framed collage of costume fabrics, signed by Elaine Paige; and signed posters of the show.

* John Gielgud's Dunhill lighter, given to him on closing night of the 1933 34 London production of Richard Of Bordeau, engraved with the show's title, opening and closing night dates, and the initials "J.G."

* A quilt made by members of the Les Miserables company.

* Record albums of The Road To Hong Kong signed by Bing Crosby; signed copy of Jerome Robbins' Broadway; signed copy of Into The Woods.

* Tickets to the The Lion King's final preview and opening night party.

--By David Lefkowitz