There should be a ton of printed material to collect for The Spider's Web (1938) and The Spider Returns (1941). Each serial had posters of different sizes and press materials (though a pressbook of Web has yet to turn up); And each of the 30 separate chapters had a movie poster and multiple lobby cards.

Spider Returns Handbill 9"x10-1/2"
(LEFT) This seems to have been assembled from various advertising clip art to be handed out at the theater.

GOOD $25 | FINE $60 | NEAR MINT $100 (Hake's)

Spider Returns Handbill 9"x12"
(RIGHT) This is the more polished of the two handbills. (Notice that part of it's design was chopped up and used on the other.) Appears to have space at the bottom for a theater's imprint.

GOOD $35 | FINE $75 | NEAR MINT $125 (Hake's)

Spider Returns Pressbook
I have never seen one of these in person, but generally pressbooks contain information for exhibitors, showing the different sizes of posters they can buy for their theater and providing clip art they can use for local advertising.

GOOD $125 | FINE $250 | NEAR MINT $450 (Hake's)

Movie Posters
These come in different sizes. Each serial title would generally have a one-sheet, three-shee, six-sheet, and banner, and each chapter of the serial would have it's own poster (all the same, except for an area for that week's photo and title). Check out the Web and Returns galleries for all the examples I could track down.

SPIDER RETURNS CHAPTER 10 ONE-SHEET, VERY FINE $625 (Me)

Lobby Cards
In my experience there are two kinds of lobby cards for both serials: A "generic" series of 8 or more cards for the whole property (probably from a rerelease), and "chapter-specific" cards for each episode. A chapter-specific group would contain one "title card" followed by a run, each using a photo from that episode. I haven't seen enough of these from either serial to say how many there are. See the Web and Returns galleries for all the examples I could find.

WEB CARDS $50-200 | RETURNS CARDS $20-100 (Guesstimate)

Press Photographs
For both serials, Columbia released a number of posed gallery shots of the main characters (separately and together), and then a series of shots for each chapter of the serial. Photographic reprints of these are pretty easy to pick up for $10 or less. Original studio-made photos are harder to come by and are highly collectible. An original is usually on heavier paper stock (showing aging), and on the back are the ink stamps of the Photographer/Company (for credit) and the Advertising Advisory Council (with approval dates written in); A caption may also be taped or glued to the back.

ORIGINAL STILLS: WEB $20-50 | RETURNS $10-25 (Guesstimate)