Profile Builder Plugin: This is the free version of the plugin. For a nominal fee, you can purchase the professional version which gives you the ability to create your own profiles. This plugin is great for adding moldings and countertops.
Toggle Units Plugin: You will need to register with Sketchucation before being able to download this plugin. Gives you a toolbar that allows you easily switch between different units of measure.
Time recording Plugin: Will track your time spent working in your SketchUp models. Good for those who need to do time-clock management.
Cutlist Plus: A great cutlist program. There are versions suitable for small and larger shops.
VCarvePro: CNC Software at a terrific price point. It's missing a few things like the ability to create labels.
Enroute: CNC Software that has a lot of the features that larger shops demand.
Sketchucation: A fantastic site for everything Sketchup!