There are many CAD applications which use parameters to 'drive' the model. You need to decide whether you want to study a mainstream application, which is used widely and will probably be more useful in the long term, or a product which is more niche in this industry. A lot of parametric CAD applications are geared towards manufacturing, such as Solidworks and Inventor, and some, like Catia can require that programming expertise mentioned in earlier replies.
Rhino is a generic 3D modelling application, and although it is a brilliant product, it isn't specifically geared to the architectural profession beyond its visualisation capabilities (and if you're getting complex, exporting data to rapid prototyping machines). If you wanted to extract some useful project information, you'd probably end up exporting a Rhino model to something like Revit, and develop it from there.
Although Revit still has many areas which need to be addressed before it can live up to the hype, it is parameter driven, and the conceptual editor added on in the last release (2010) is very capable. You can see some examples of what can be achieved by messing around with parameters at http://buildz.blogspot.com/ and bimtroublemaker.blogspot.com
Given the investment Autodesk is pumping into Revit, like it or not, it'll probably be the industry standard design application for architects within the next five years, so my advice would be to go where the money is!