From website:
Welcome to $1 Adventure Frameworks!
$1AF makes sweet mini adventures - or more accurately what I like to call "Adventure Frameworks" - stand alone, drop in adventure 'skeletons', made to facilitate sandbox style play - for $1.
Each adventure framework is set in a generic medieval or ancient fantasy location, with enough meat to enable the GM to improvise details and adapt to player choices.
System wise, these adventures use the Low Fantasy Gaming RPG (an old school/modern mix d20 based game), but are easily adapted to any d20 system.