Low-level macros: MinimalSyntaxCaseCowan, explicit renaming, syntactic closures, R6RS syntax-case, SRFI 72.
More syntax-rules extensions: SRFI 139
Macro uses in syntax definitions: SRFI 147
Syntax parameters: SRFI 139
Matching: MatchingWise
Combinators: CombinatorsCowan
cond guards: SRFI 61
Lambda*: BeyondCurryingHemann
Void: VoidCowan
Named parameters: NamedParametersCowan or SRFI 89
and-let*: SRFI 2
Generalized set!: SRFI 17, possibly plus Srfi17ExtensionsCowan
receive: SRFI 8
rec: SRFI 31
Cut/cute: SRFI 26
Loops: SRFI 42 or Riastradh's foof-loop or Chibi loop
Generic accessors/mutators: SRFI 123
Conditions: ConditionsCowan
Restarts: RestartsRiastradh