Decal Manager is a commercial MAXScript that allows you to quickly load and save decal sets, save geometry combinations that you can place and attach decal objects to screen for ease of access (you can arrange them on screen how you please with 'edit' mode), as well as having a snap to surface decal place mode, the ability to remember scale per decal and auto-parenting to target geometry.

Decal Manager is available for Max 2018 to 2022 and costs £60. There is also a non-commercial version available for £10.

Changes for vv2020.2.5 - 11.13 are:
- Fixes issues when rendering with render elements, Cryptomatte, LDR/HDR, EXR
- Fixes RailClone Mesh updates in Direct mode
- Adds RailClone default settings to Preferences

OctaneRender is available for Max 2013 to 2022 and costs €699 per year. A demo version is available here.

Changes for v7.2.8.28868 are:
- Multiplier nodes can now be baked, preserving input to output shape relationship
- Fixes a Generate Strand Data crash when switching channel type to Per-Vertex
- Fixes a Generate Strand Data crash when removing channels that have been renamed
- Fixes a Surface Comb crash when switching to Mesh Vertex algorithm when curves are used
- The per-sink controls are now disabled when no sink is selected
- Fixes incorrectly transformed Control Points when using rotation or scale tools
- Fixes incorrectly assigned weights when using multiple control points
- Multiplier maps now work in the Surface Comb
- Fixes Select by Group not working when using the Select brush

Ornatrix is available for Max 2014 to 2022 and costs $599. A demo version is available here.

Changes for v0.16128 beta are:
- Adds rotation align settings to the Array operator
- Adds a 'delete keys outside of time range' option to the tyFlow spinner right-click menu
- Adds an export groups option to operator filters
- New Bounds Fracture operator options for more control over which bounding box axis is sliced
- Adds tfMatrix rotation functions to the Script operator
- Adds an interpolation curve control to the tyLooper modifier
- Adds a seed by time option to the Rotation operator
- Fixes an issue with VRay proxy data loaded from .abc files with multiple mesh sub-elements
- Fixes timing modes not working correctly if sim time step set to certain values
- The Birth Objects operator now respects the internal scale multiplier of input VRayProxies
- Birth operator particle count over time is now independent of simulation time scale
- Tidies up the Voronoi Fracture operator rollouts
- Fixes tySwitcher settings in the Export Particles operator from not working correctly
- Fixes a Birth Skeleton crash that could occur when 'cull tiny junctions' is enabled

Changes for vv2020.2.5 - 11.12 are:
- Adds VDB grid display in the Max viewport with multi channel support
- Fixes an issues with light visibility / Clay mode
- Adds the missing Color clay mode
- Fixes texture updates in the Max viewport
- Fixes animated material updates being disabled in the MatEditor when texture cache is disabled
- Fixes the animated 2D transform UI showing the same values for X and Y
- Fixes AOV graph editor changes causing errors or wrong updates
- Fixes saving of Cryptomatte passes, as EXR when animated, or as HDR RGB image
- Fixes rendering of Cryptomatte passes in LDR with standard render
- Disables saving of Deep Image and Cryptomatte with normal Render when Save file is unchecked

OctaneRender is available for Max 2013 to 2022 and costs €699 per year. A demo version is available here.

Changes for v7.0 include:
- The Flow operator now integrates a full grid based Material Point Method
- Multiple new operator nodes offer a 100% procedural control of any MPM effects in tP
- New Cellular node creates procedural volumetric 3D patterns and groups them in individual cells
- The Cellular node now also has a Voronoi pattern alongside the Circular and Chip patterns
- Adds new DX hardware accelerated particle viewport display method to enhance viewport feedback
- Memory management and multi-threading has been enhanced
- Adds a full commercial license of finalRender, valued at US$ 294, for free
- A full list of new features can be found in the What's New section of the online manual

thinkingParticles is available for Max 2020 to 2022 and costs €600 per year. A demo version is available here.

Changes for v2.001 are:
- Adds Pmodifier to passgroup
- Adds instanced passes
- Adds a Selection button to the object selection method UI
- New Make Unique function keeps instances among the selected pmodifiers
- New Select Instanced Node function lets you select all instances of the selected pmodifiers
- Generate Pass(group) Per Camera now supports passgroup (Make Passgroups)
- Generate Pass(group) Per Camera now supports Prefix/Suffix
- Adds an option to save the entire tree including passgroups for Save...
- Improves the *Params pmodifier Material support
- The treeview node highlight has been refactored
- Adds override mtl/mask related parameters to the Renderer Params exclude list
- Special characters in the Selection Set name no longer crashes renderStacks
- The save rs xml file function now saves passgroups properly
- Fixes the material/map assignment popup crashing when it is a map
- When the Material/Map value is set to undefined/clear, it now works as expected
- Fixes the accumulative pmod selection indicator message

I just updated the links in the post, I had them completely wrong!

renderStacks is available for Max 2015 to 2022 and costs $59.99 per year. A demo version is available here.

Changes for v2.39 are:
- The 'Reset' button in the Camera Name group will now force the script to shut down
- Renaming multiple cameras is now faster, especially with a large number of selected cameras
- Removes the 'Output Location' text and reorders the bottom layout of the script
- The Smart Camera Rollout is now smaller by 4% (595px -> 570px)
- Adds an 'Invert' button to the Render Setting group: inverts the resolution and aspect ratio
- Adds a 'Desktop' button to the Batch Render group to select the desktop as an output folder

Smart Camera View is available for Max 2012 to 2022 and costs $7.99.

Changes for v3.3.1 are:
- Adds a new Recovery Tools section
- Adds an option to clear missing plugins
- New virus signatures: PhysX Plugin Mfx, Desire FX CA, AlienBrains, ALC2, AD Web CA, Kryptik CA
- Adds a multi-language interface (English, Russian, Ukrainian, Polish, Vietnamese, Chinese)
- Adds a Batch Disinfect files feature for Selective Scan
- By default clear options in rollout Main are now disabled
- Updates the UI for some rollouts and the installer

Prune Scene is available for Max 2012 to 2022 and costs $7. A demo version is available here.

Changes for v10.1.18.5 are:
- Mesh Lights instantiated by particles or Mograph are now properly importance sampled
- Rectangle light sources are now less noisy
- Adds Direct/Indirect Lighting scale factors for light sources
- Adds light pass, material layer and Direct/Indirect scale factors to the Emission material
- Fixes various small bugs for light sources
- Fixes an incorrect UVW tag parser for Forester trees scattered by the Cinema 4D cloner

NAG ALL (Automatic Library Lister) is a Python script that specializes in automating the process of organizing digital library assets. After using the script, you will have a highly organized library consisting of Max files and their related preview images. The 3D library can be used manually (drag and drop), or for bridging with asset management plugins such as Project Manager, Connecter, or Autodesk Assets Library.

NAG ALL PRO is available for Max 2018 to 2022 and costs €99.

Changes for v1.2 are:
- Adds support for Max 2022
- Minor bug fixes

Aq Bullet is available for Max 2015 to 2022 and costs $245. A demo version is available here.