  The most classical version of the Schwarz lemma involves the behavior at the
origin of a bounded, holomorphic function on the disc. Pick's version of the
Schwarz lemma allows one to move the origin to other points of the disc.
  In the present paper we explore versions of the Schwarz lemma at a boundary
point of a domain (not just the disc). Estimates on derivatives of the
function, and other types of estimates as well, are considered. We review
recent results of several authors, and present some new theorems as well.
