As a Mac user there once were few choices when it came to CAD/BIM applications. With Apple's popularity, more and more formerly Windows only CAD apps are finding their way back to the Mac. The big fish in the pond of CAD for Mac is Autodesk with their AutoCAD for Mac, which after a 17 year gap, came back to the Mac in 2011. Recently joining this surge was BricsCAD (See New CAD + BIM Options for Mac).
But the question remains, what's the best CAD/BIM software for the Mac? Well, the team over at MacHow2 has compiled a comprehensive list, with detailed explanations for each option that will help you define what your needs are and select the application that will best fit those needs. Check out their excellent summary of "The Best CAD Software for Mac" post.
To continue the conversation, join the Apple for Architects Google+ Community for help from those that use many of these applications.