I downloaded the source for the IFrame module (IFrame_04.03.00_Install.zip), unzipped it, and added the module definition using the Host account and the Module Definitions page.  Then, I added the IFrame module to the VS 2008 solution I'm working with underneath the DesktopModules folder.  When I try to build the solution, it gives me declaration errors on the EditIFrame and IFrame controls, specifically referencing undeclared objects.  There is an Imports statements DotNetNuke.Modules.IFrame.Domain) in each of these controls that is flagged as not containing any public member or not able to be found, yet that namespace exists in IFrameParameter.vb, IFrameParameterCollection, and IFrameParameterType.vb with public members in each.  This is my first attempt at modifying one of the downloadable modules, so I have probably overlooked something basic.

 Also, here is a nice tutorial on how to develop a Survey Module by the great Michael Washington - it uses the same architecture, basically,  so it should be very helpful