PEET is subtomogram averaging package developed and maintained by the University of Colorado at at Boulder. PEET is free, open-source, and is supported on Linux, MacOS, and Windows. Please see the link above for binaries, source code, and documentation.
PEET is distributed as a separate package but integrates with and is typically used in conjunction with the Imod tomography and modeling package. PEET is written in Matlab® but does not require a prior Matlab® installation to use. A graphical user interface provides easy access to basic operations, while more advanced operations and customization are supported via the command line with optional shell or Matlab® scripting.
PEET was first described in Nicastro et al, 2006.