Gamma World Game Rules 4th Edition - This version of Gamma World is from 1992 and is probably the most old school D&D compatible of the bunch and is where ascending armor class was first introduced. $9.99 for PDF, $24.99 for print version
Gamma World: Gamma Knights - Really more of a board game than supplement. $4.99 for PDF
S4 The Lost Cavern of Tsjocanth - Presumably now updated for the print version ($9.99) or PDF + Print ($11.99). This is one of my favorite modules
Book of Lairs: Abandoned Places - 13 monster lairs for ACKS. $3.27 and 36 pages.
The Barbarian King - Adventure from Melan/Gabor Lux, probably one of the most original (in a good way) adventure designers in the OSR. $4 and 24 pages.
Dolmenwood Rogues Gallery Vol 1 - Some pregens for LL. PWYW
Friday Enhanced Map 7-13-18 - Part dungeon, part cave. $1
Thief Skills Totaliser for LL - Spreadsheet or something because apparently for some it's harder to copy numbers from a table in a book than to use a spreadsheet, I guess. PWYW