Although it also names a couple of hardware companies, S3's main referent in computing is to the "Simple Storage Service" [L1 ] among Amazon Web Services [L2 ].
Darren New has been working on a Tcl interface Amazon S3.
Dossy has "some basic Tcl code that speaks to S3 in AOLserver."
Michael Andrews might be working on "nss3" ...
S3 is also the name of an Algol 68 based system programming language used on ICL VME (Virtual Machine Environment) mainframes [L3 ].