  Since 2008 the Fermi/LAT instrument has delivered highly time-resolved
gamma-ray spectra and detailed variability curves for a steadily increasing
number of AGN. For detailed AGN studies the Fermi/LAT data have to be combined
with, and accompanied by, dedicated ground- and space-based multi-frequency
observations. In this framework, the Fermi AGN team has realized a detailed
plan for multi-wavelength campaigns including a large suite of cm/mm/sub-mm
band instruments. Many of those campaigns have been triggered, often for
sources detected in flaring states. We review here a few interesting results
recently obtained during three such campaigns, namely for the flat-spectrum
radio quasar 3C 279, the Narrow Line Seyfert 1 PMN J0948+0022 and quasar 3C
454.3.
