We have used the 20 largest radio continuum catalogues contained in VizieR (CDS) to determine radio continuum spectra between wavelengths of 2cm and 1m. For 67,000 out of the 3.5 million catalogued sources we could extract radio spectra with measurements at at least 3 independent frequencies. These have been validated by comparison with existing spectral indices from the literature. Our radio spectra data base was searched for Gigahertz peaked source candidates, which we then observed quasi-simultaneously with the Effelsberg 100-m radio telescope at 6 cm (4.85 GHz), 2.8 cm (10.45 GHz), and 9 mm (32 GHz). This is an efficient procedure to discover new Gigahertz peaked sources, which are believed to be AGNs at the beginning of their radio evolution. We are generalizing the method by using VO capabilities to (i) identify pertinent radio catalogues in the VO registry using Uniform Content Descriptions (UCDs), (ii) extract relevant data, and (iii) normalize these for the determination of radio spectra. Software allowing semi-automated information retrieval is being developed within the framework of the European VO-TECH project. The potential usage of all available radio catalogues will strongly increase the number of independent radio source cross-correlations and radio spectra. The results are progressively being made available to the community through the CDS services.