Scheme Requests for Implementation (SRFI) provide Scheme users portable, useful code not necessarily present in typically minimalist language implementations. SRFI are well documented on the dedicated website, but it is not always clear what is the best or most idiomatic solution for a given application. The list below is strongly based on ongoing discussions for the Revised 7 Report on the Algorithmic Language Scheme (R7RS).
(Of course not all of the following SRFI may be distributed or packaged for a given implementation. Note that SRFI documentation often refers to similar SRFI that may be instead available for the given implementation. For instance, currently SRFI 125 for hash tables is not available as a CHICKEN Scheme package, but the older SRFI 69 is.)