Yesterday, we held a training for RF programming in LabVIEW. (download the presentation)
As part of that training, we covered the basics of signal modulation, which can be a tricky thing. Luckily, an RF engineer at NI created the Baseband Developer's Resource Kit, which is a free download at:
http://digital.ni.com/express.nsf/bycode/baseband
This kit includes an executable (requires the LV run-time engine, which installs for free with the kit) which demonstrates how I/Q data is generated, and how various analog and digital modulation schemes code information using this I/Q data. The kit also includes all of the source code (in LabVIEW), and several white papers on RF measurements. This is a great tool if you are teaching, or learning, about RF communications and wireless testing.

