The lists below refer to people or labs doing research on passerines (as well as other organisms) that I think is interesting, or important, or both. I have crudely split them up into clusters, but recognize that many researchers and research programs cross boundaries, and you (or they) may disagree with the primary categorization listed here.
Passerine Evolutionary Biology and Phylogeny
Benkman Lab, University of Wyoming - Loxia evolution and ecology
Badyaev Lab, University of Arizona
George Barrowclough, American Museum of Natural History - Junco, Turdus migratorius, warblers
Edwards Lab, Harvard University
Sorenson Lab, Boston University
Frederick H. Sheldon, Museum of Natural Science, Louisiana State University
Robb Brumfield, Museum of Natural Science, Louisiana State University
Martin Lab, University of Montana - Passerine nesting biology and life history evolution
Irby Lovette, Cornell University
Robert E. Ricklefs, University of Missouri, St. Louis
Kevin Burns, San Diego State University
Carlos Daniel Cadena O., University of Missouri, St. Louis
J. Van Remsen, Jr., Museum of Natural Science, Louisiana State University
John Klicka, M. Barrick Museum, University of Nevada, Las Vegas
Gary Voelker, University of Memphis
Kevin Omland, University of Maryland, Baltimore County
Alice Cibois, Natural History Museum of the City of Geneva
Amy Driskell, University of California, Davis
Anthony Bledsoe, University of Pittsburgh
Per Ericson, Swedish Museum of Natural History
Jordan Price, St. Mary's College of Maryland - Oropendola phylogeny and behavioral evolution
Trevor Price, University of Chiago - Evolution and ecology of Old World warblers
Joel Cracraft, American Museum of Natural History
Early Bird, The Field Museum of Natural History
Spicer Lab, San Francisco State University
Passerine Ecology and Physiology
Williams Lab, Ohio State University - Comparative physiology and life histories of Alaudidae
Hau Lab, Princeton University - Physiology, ecology, evolution...
Tieleman Lab, University of Groningen - Comparative physiology and life histories of Alaudidae and other passerines
Passerine Neurobiology
AvianBrain.org - Information on passerine brain structure and research
Nottebohm Lab, Rockefeller University
Goodson Lab, Indiana University, Bloomington
Eliot Brenowitz, University of Washington
Margoliash Lab, University of Chicago
Timothy DeVoogd, Cornell University
Gregory Ball, Johns Hopkins University - Sturnus vulgaris
George Bentley, University of California, Berkeley
MacDougall-Shackleton Lab, University of Western Ontario
Michael Brainard, University of California, San Francisco
Allison Doupe, University of California, San Francisco
Passerine Behavior
Bioacoustic Research Program, Cornell Lab of Ornithology - Sandra Vehrencamp et al.
Bird and Mammal Acoustic Communication Group, University of St. Andrews - P.J.B. Slater et al.
Animal Behavior Farm, Indiana University - Meredith West and Andrew King, Molothrus behavior
Behavioural Ecology Group, University of Cambridge - Dunnocks and warblers and cuckoos, oh my! (no, cuckoos are not passerines, but hey)
Behavioural Ecology Research Group, Oxford University - Corvus tool use, Sturnus behavior, Molothrus hippocampus
Pied Babbler Research Project - the Kalahari, social passerines...what's not to love?
Hill Lab, Auburn University - Carpodacus and more
Mark Hauber, The University of Auckland - Molothrus behavior
Haven Wiley, University of North Carolina, Chapel Hill - Campylorhynchus nuchalis et al.
John M. Marzluff, University of Washington - Corvus
Russell P. Balda, Northern Arizona University - Social behavior and memory in New World jays and other corvids
David Westneat - Agelaius phoeniceus behavior
Ken Yasukawa, Beloit College - Agelaius phoeniceus behavior
Searcy Lab, University of Miami - Agelaius phoeniceus behavior
Stephen Rothstein, University of California, Santa Barbara - Molothrus behavior
Jordan Price, St. Mary's College of Maryland - Campylorhynchus nuchalis vocal learning, oropendola and cacique vocalizations
Dan Mennill, University of Windsor - Poecile atricapilla and Thryothorus rufalbus vocal behavior
Bridget Stutchbury, York University - Mating systems, tropical passerines.
Laurene M. Ratcliffe, Queens University - Poecile vocalizations
Ketterson/Nolan Lab, Indiana University - Mating systems and life history, steroid hormones.
Podos Lab, University of Massachusetts, Amherst - Song and morphology of Darwin's finches and Melospiza
Nowicki Lab, Duke University - Melospiza vocal behavior
Andrew Cockburn, Australian National University - Australian birds, cooperative breeding
Linda Whittingham, University of Wisconsin, Milwaukee - Behavioral ecology of Tachycineta, Troglodytes, and Geothlypis
David McDonald, University of Wyoming - Chiroxiphia, Aphelocoma, and others
Passerine Hormones
Schlinger Lab, University of California, Los Angeles
Wingfield Lab, University of Washington
Stephan Schoech, University of Memphis
Passerine Plumage and Coloration
Kevin McGraw, Arizona State University
Richard O. Prum, Peabody Museum of Natural History, Yale University