We have started a subscription to Signal Transduction Knowledge Environment (STKE), one of the most highly-requested titles via Document Delivery over the past few years.
From the STKE website:
"Signal transduction is the study of how cells control their own and each others' behaviors through chemical signals. Signal transduction research is an intensely active field of biomedical research and is of interest to a broad array of scientists. Science's STKE should be useful to the scientists who specialize in signal transduction, as well as the many scientists who need to follow and apply the current findings of this field even though their primary interest may not be in signal transduction mechanisms themselves."