Plugin Suites
Families of plugins by the same authors

Available for all platforms

GVST

A set of simple VST effects, most known for the GSnap (auto-tune) effect.
GVST - Packages
Download page

swh Plugins

A set of LADSPA effects.
plugin.org.uk

Available for Windows

Reaplugs

A selection of some effects found in Reaper.
REAPER | ReaPlugs
Download page

Available for macOS

Available for Linux

Calf Studio Gear

An LV2 plugin suite featuring a wide array of plugins for audio mixing and mastering. As of version 0.90.0 there are 47 plugins in the suite.
Note: The virtual instruments included are not supported in Audacity.
The Calf plugins can be found in the repositories of most Linux distributions, additionally, compilation instructions can be found here:
Calf Studio Gear - GNU/Linux Audio Plug-Ins