Bezier Surface Modelling for SketchUp
It was supposed to be my second commercial extension, but I've not been able to maintain it. Recently I've focused open my subdivision extension.
Instead of letting it become vapour-ware I'm releasing it for free as-is: http://extensions.sketchup.com/en/content/bezier-surface
Note that this isn't a finished product so it has it's limitations and bugs. It's to be considered a beta product.