Marlin Harmony's webpage has an alternative description of microwave spectroscopy that is worth checking out.

The Journal of Chemical Education offers a tutorial package in micorwave spectroscopy,  it includes diagrams and free software.

Dr. Novick at Wesleyan University has prepared a searchable index of weakly bound complexes characterized with microwave spectrocopy.

For a list of recommended frequencies for use in interstellar spectroscopy see NIST's page of rest frequencies.

The Jet Propulsion Laboratory (JPL) provides many services of interest to spectroscopists, including software for download and a spectral line catalogue.

The Jet Propulsion Laboratories also do microwave spectroscopy,  Dr. Kuiper's work in Interstellar Microwave Spectroscopy is presented here.

The International Astronomy Union (IAU) has just designed a web page tailored towards astrochemists.