Historians attempting to get at the Jewish peasant Jesus behind the Gospel portrayals adopt several criteria — some more valid than others — in order to assess probabilities in what the actual Jesus said or did (among these are the criterion of multiple and independent attestation; the criterion of dissimilarity; the criterion of embarrassment; and the criterion of historical plausibility). Mark Goodacre has several very well-done posts on neglected criteria for the study of the historical Jesus:

Historical Jesus Forgotten Criteria I: Accidental Information

II: View Common to Friend and Foe

Did Jesus have a house in Capernaum?

Some more historical Jesus online:

    Mark G. himself has collected links to resources here.
    The PBS website (for From Jesus to Christ) has several scholars’ thoughts on the historian’s task in reconstructing the historical Jesus.