Free tools for making Flat Text and Flat Leader objects
Flux helps you collaborate with other SketchUp users, and connects SketchUp with other popular design tools like Revit, AutoCAD, Dynamo, Excel, Google Sheets, 3ds Max and Grasshopper using the cloud instead of files.
Graphical 3D 'inside-plan' inventory, design, bill-of-materials calculation and facilities maintenance using Excel spreadsheets database
A complete landscape architectural add-on to create planting and site plans
Designed to be very similar to Photoshop's layers panel. It adds the ability to group layers, sort them, lock them, hide/collapse groups, etc.
Parametric Urban Design inside SketchUp!
3D layouts creation for paving, flooring, tiling...
OpenStudio is a cross-platform (Windows, Mac, and Linux) collection of software tools to support whole building energy modeling using EnergyPlus and advanced daylight analysis using Radiance.
BIM + VDC + Parametric modeling + Estimate
For AEC industry professionals, Product Connect is a flexible takeoff & reporting solution for SketchUp.