I loved these DC 100-pagers when they came out back from 1971-1975, a mixture of great new material, as well as reprint material that spanned from the 1940's to the late 1960's, that gave a great sampling of the era prior to 1972 when I began collecting. An era where there were no comic shops for back issues, few comics conventions, and mail order was pretty much your only option to get back issues.
I recently went through my collection, as well as ads and comics.org, and tried to draft a complete list of 100-page issues:
ACTION COMICS
437 443
ADVENTURE
416 (also DC-10)
BRAVE & THE BOLD
111 112 113 114 115 116 117
BATMAN
238(also DC-8) 254 255 256 257 258 259 260 261
DETECTIVE COMICS
438 439 440 441 442 443 444 445
FLASH
214(also DC-11) 229 232
JUSTICE LEAGUE
110 111 112 113 114 115 116
HOUSE OF MYSTERY
224 225 226 227 228 229
DC 100-PAGE SUPER SPECTACULAR (the title that started the 100-page issues)
DC-4(WEIRD MYSTERY) DC-5(LOVE STORIES) DC-6(JLA, JSA) DC-8(also BATMAN 238) DC-9(also OUR ARMY AT WAR 242) DC-10(also ADVENTURE 416) DC-11(also FLASH 214) DC-12(also SUPERBOY 185) DC-13(also SUPERMAN 252)
(and continuing as
100-PAGE SUPER SPECTACULAR in 1973: )
DC-14 DC-15 DC-16 DC-17 DC-18 DC-19 DC-20 DC-21 DC-22
OUR ARMY AT WAR
242(also DC-9) 269 275 280
SHAZAM
8 12 13 14 15 16 17
SUPERMAN
252(also DC-13) 272 278 284
SUPERMAN FAMILY
164 165 166 167 168 169 170
SUPERBOY
185 202 205
TARZAN
230 231 232 233 234 235
UNEXPECTED
157 158 159 160
WITCHING HOUR
38
WONDER WOMAN
211 214
WORLD'S FINEST
223 224 225 226 227 228
YOUNG LOVE
107 108 109 110 111 112 113 114
YOUNG ROMANCE
197 198 199 200 201 202 203 204
That's my best list of the 100-page issues (excluding the shorter 64-page giants that followed on many of these titles, such as BATMAN, TARZAN FAMILY, SUPERTEAM FAMILY and a few scattered others.)
I count approximately 111 of the 100-page issues, of which I have 60. Most of the romance, mystery, SHAZAM and Superman-related titles I don't have.
In a time before comic shops and readily available back issues, these books were pure magic, and a great window into the whole of comics history.