yeast: Yeast protein interaction network
Description
Comprehensive protein-protein interaction maps promise to reveal many
  aspects of the complex regulatory network underlying cellular
  function.  This data set was compiled by von Mering et al. (see reference below),
  combining various sources. Only the interactions that have 
  high and medium confidence are included here.
source
The data was downloaded from
  http://www.nature.com/nature/journal/v417/n6887/suppinfo/nature750.html.References
Comparative assessment of large-scale data sets of protein-protein
  interactions. Christian von Mering, Roland Krause, Berend Snel,
  Michael Cornell, Stephen G. Oliver, Stanley Fields and Peer
  Bork. Nature 417, 399-403 (2002)