ShapeGen is now available for $L100 at SLExchange.
ShapeGen builds cylinders, cones and spheres larger than 10 meters by rezzing and combining box prims. You can set colors, alpha, textures and texture scale for each side of the shape. Just place ShapeGen at the center of the shape you want to make and give it commands over a private chat channel. Settings for cylinders are updated on the fly as you watch, allowing you to adjust your design in place. Full instructions are included in a note card inside the tool.
ShapeGen can be used to make rounded shapes such as a dome or just to arrange prims geometrically such as in an octagon or pentagon. The more prims you use, the smoother the shape.
For an excellent example of what can be done with ShapeGen visit Cubey Terra's Aerodrome in Abbotts next to the Cordova sandbox.