Simple Plugin Installer by ThomThom

Sketchup plugin creator ThomThom has created a great plugin that allows easy installation of RBZ, ZIP, and RB files. After the introduction of Sketchup 2014, it became somewhat of a hassle to install RB files so this nifty plugin is greatly welcomed.

Simple Plugin Installer by ThomThom

Viewport Resizer by Eneroth3

Viewport resizer by Eneroth3 is a great plugin that gives you the ability to export an image from Sketchup at any image aspect ratio you want.

Sketchup Extension Warehouse

How to Install Tools, Plugins, and Extensions in Sketchup via Designer Hacks

Designer Hacks has created a great tutorial video explaining how to install Tools, Plugins, and Extensions in Sketchup.

via Designer Hacks

Soap Skin & Bubble Plugin

Sketchup is a great tool for modeling all sorts of shapes and objects.  One of its biggest drawbacks is that it has a hard time modeling organic shapes with NURB attributes but luckily it doesn't have to stay that way any longer thanks to the Soap Skin & Bubble plugin.