Release 5 scripts are already surfacing:
Layer Bar v1.0 by Herman Saksono - Extends 3ds max 5's layer system, simplifying its ui at the same time.
Nature Painter v1.0 by Herman Saksono - Create grass and pebbles using a brush based interface.
PolySculptTool v1.0 by Herman Saksono - Sculpt polygon objects using a brush based interface.
Also of note (R4 compatible):
TreeMatoGraph v0.2.4 by Borislav Petrov - A graphical interface to the Material Editor. Lets you visualize and edit maps/materials relationships and quickly navigate the Material Editor.
SpreadSheet Editor v0.4.2 by Borislav Petrov - Provides a flexible and highly customizable base utility for mass-displaying and manipulating object properties.

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More great scripts (R4 compatible):
Tree Maker v5.0 by Shawn Lewis.
MJPolyTools v1.0 by Mikkel Jans - Poly modelling tools including: Connect Verts / Edges, Connect Edges X, Multi loop Split, Multi Loop Split X, Multi Loop Select, Loop Split, Loop Split X, Edge To Quad, Divide Edge X. Check out the website for detailed diagrams.