Perhaps the most fascinating command new to AutoCAD 2007 is Sweep. It takes (just about) any shape and extrudes it along a path. (The old Extrude command was fussier than its new Sweep replacement.)
Above, I swept the red spline along the black one (the path), and told Sweep to twist the path by 90 degrees, and then displayed it in Conceptual visual style with facets and isolines turned off. Another simple trick is to sweep a circle along a helix path to create coiled springs.