IMSI has an OS X version of TurboCAD for the Mac.
There isn't much detail -- such as is this a port, or a new program with the TurboCAD label? Reading between the lines, this first version is 2D only: "IMSI plans to release a second, 2D/3D version of TurboCAD for Mac OS X later this year." Another hint: it comes with a 3D-2D converter for flattening 3D drawings.
The Web site has not yet been updated with this new information. Price is US$99.
Dassault Systemes also ports Cosmic Blobs to the Macintosh -- 3D graphics software ever for kids. Available in July for US$45.
New version 1.1 for PC and Mac adds movie file capture; improved content; expanded user interface. There'll be expansion packs in the fugure: Critter Chaos is included free, and has animal-themed models, textures, decals, animations, and background options.