What's on the design block?
The season, first of all, bears the literal ''stamp'' of architecture. Yesterday, Sept. 30, the final block of major buildings on postage stamps was issued to celebrate the 125th anniversary of the American Institute of Architects.
The latest batch of ''Architecture USA'' stamps updates a philatelic enterprise that began with work by Jefferson and Bulfinch, moved in batches of four through Victorian Gothic and turn-of-the-century Gold Medal winners, and winds up this week with three modern monuments.
Some 165 million stamps will depict Fallingwater at Mill Run, Pa., by Frank Lloyd Wright; the Illinois Institute of Technology in Chicago by Ludwig Mies van der Rohe; the Gropius House in Lincoln, Mass., by Walter Gropius (with Marcel Breuer); and Dulles International Airport outside Washington, D.C., by Eero Saarinen.
As if to parallel the glut of skyscrapers rising in Manhattan, the Museum of Modern Art will offer the trendiest architecture exhibition of the next months.
''Skyscraper,'' Jan. 26 through March 22, will focus on three of the latest high-rise spectacles. Model drawings and construction photos of three of the breed will amplify the design process. Right now, however, curator Arthur Drexler will not cite the names of the chosen few. A good guess, however, is that Cesar Pelli's controversial cliff dweller now under construction for the museum itself will be one of the three cliffhangers.
While ''Le Corbusier's Sketchbook,'' reviewed here, makes a stop at the National Academy of Design in New York through Oct. 31, another unusual exhibition begins its United States rounds this month.
''Rudolph Steiner's Architectural Impulses'' brings the expressionistic design of the philosopher-educator to Harvard's Gund Hall and Hilles Library through today, then to the Rhode Island School of Design and elsewhere.
''So long,'' Steiner said, ''as we are compelled to hold our meetings in halls whose forms belong to a declining culture, our work will unavoidably also more or less share the fate of all that is caught up in its decline.''
At 46, Steiner came to the conclusion that color and shape followed function on a spiritual level. He translated the sentiment into an extravagant architecture.
Educator, philosopher, scientist, this architect of matters of the nonmaterial shaped an architecture of expressive, almost bizarre arrangements because, as he put it, ''You are only able to express a true harmony of the soul when you are surrounded with colors and forms that express your most valued thoughts, feelings, and instincts.''
So Arne Klingborg, the organizer of this strange but haunting exhibition, described the show launched for the 50th anniversary of Steiner's creation of the Goetheanum in Sweden a couple of years ago.
The architectural environments for life upon the ''wicked'' stage also gets some attention this season.
An exhibition of ''American Picture Palaces'' will run Nov. 23 through Feb. 27 at the Cooper-Hewitt Museum in New York. Everything from furnishings and photos to a sign from the Roxie will display these endangered but endearing extravaganzas.
Singular architects will also appear on the fall exhibition agenda. ''Uncommonly Frank,'' a traveling show of the houses and offbeat furnishings of California architect Frank Gehry lights at Boston's Institute of Contemporary Art through Oct. 31.
The Max Protech Gallery in New York, which prompts architects to shake out their sheafs of drawings on a regular basis, will offer next month the work of Venturi Rauch & Scott-Brown, known for espousing ''complexity and contradiction.'' The gallery will also feature the intellectually rigorous design work of John Hejduk in February.
Frank Lloyd Wright will appear three- and two-dimensionally, so to speak, when the restored living room he designed in the Francis Little home from 1912- 1915 opens at the Metropolitan Museum of Art in New York, in the American Wing, Dec. 5.
To accompany the slow and controversial installation from the demolished building, the museum will offer 60 its own Wright artifacts: furniture, ceramics , fragments, graphics, and other drawings will appear in conjunction with the opening from Dec. 5 to March 1.
Moving from private to public spaces, the Municipal Art Center in New York is offering a view of ''Culture Stations,'' subway stops as designed objects.
Another anniversary offers this New York center a chance for still another exhibition: The 50th year of the Rockefeller Center will be celebrated with photos, memorabilia, and some video displays to recall the origins of the megacenter that predated all megacenters half a century ago.