This question has come up quite a few times, recently. Extensions are wonderful and we know that they help accelerate your workflow, but which ones help the most? The real answer depends on your workflow.
In an effort to get a conversation started around extensions related to specific workflows, we are going to start with a list of helpful extensions we have heard about within the community.
1001 Bit Tools - Freeware with a professional version available. 1001 Bit Tools is a suite of tools that simplify the drawing of geometry associated with drawing a structure in 3D.
Profile Builder - If you plan to draw any walls, railings, or fences, you need to check out Profile Builder. Now in version 3, Profile Builder can be thought of "Follow Me" on steroids. It allows you to put together arrays of geometry that are duplicated along the stretch of a user-defined path.
Framer - Not everyone puts framing into their models, but if you do then you should take a look at Framer. Created by the same guy who created Estimator for SketchUp, Framer makes it quick and easy to add wall framing into your model.
Vali Instant - There is a LOT to look at here. With extensions that do everything from cladding to curbs, the Vali Instant suite of extensions adds great looking detail to your model.
Medeek Extensions - Originally offering a truss layout tool, the extensions from Medeek have multiplied into a suite of tools that will help you to frame an entire structure from foundation to peak.
There are a lot of great extensions out there, and I am sure there are others who have a list that differs from the one above, but these were the ones that we thought of when asked.
Do you have a different set? Let us know what we missed.