Lilly MedChem Rules
In late 2012 Robert Bruns and Ian Watson published a paper entitled Rules for Identifying Potentially Reactive or Promiscuous Compounds. These 275 rules encapsulated 18 years of Drug Discovery experience and are used to identify potentially troublesome molecules.
The code to implement these rules was kindly made available by Ian Watson on GitHub unfortunately my initial attempts to compile this failed, but Matt was able to provide a patch to compile under Mac OSX (Mavericks) using Clang. Whilst this would be sufficient he then went the extra step and made it available via HomeBrew.
You can read more here.