This is my code to compute the Raman spectra (resonant and non-resonant) with NWChem.
The subroutines attached were written within the version 5.1.1, there are a few changes respect 6.x and 7.x. The code has to be updated.
There are significant differences between my version and the the provided by the most recent version in nwchem-6.0 (May 2011),
My version computes the Raman intensities at the same time with the vibrational/frequency analysis, and not at posteriori, thus, computes all the cartesian displacements, what it means is that computes all the vibrational modes, at once.
Another significant difference resides in the capability of the discretization of the vibrational problem by subgroups of tasks, or subtasks. This is useful when you have hundreds of computer nodes and limited inter communication resources among them.
Besides to the vibrational analysis, this also works as a template for other "discretizable" problems.
Also, in useful programs you can find my program in phyton to create nice plots of the Raman spectra by the convolution of the active peaks employing Lorentzians funtions.