This table lists alternatives (packages and modules which can do the same or similar tasks) and extensions (code snippets and libraries which build on top rather than replace), for a range of Haskell packages and modules. Your help is appreciated in expanding it.
When editing this table, please try to keep it in alphabetical order (by package name, then by module name), maintain reflexivity (except with the package named "base") and create relevant links wherever possible. Please also try to avoid duplication and excessively long entries in the table, by creating wiki pages where necessary.
It is debatable whether a new version under a different name should go in the "alternative(s)" column or the "extension(s)" column. Perhaps it should go in the "extension(s)" column if it is (mostly) backward-compatible, and otherwise in the "alternative(s)" column.
Note (1): base here, refers to GHC's base package, unless otherwise stated.