gridgen is a C code that provides a command line utility for non-interactive generation of multi-corner quasi-orthogonal grids inside simply connected polygonal regions. It is based on the CRDT algorithm that makes it possible to handle regions with elongated channels in a numerically robust way.
Here are some example grids from the gridgen package. You can also find a number of grids generated with gridgen for operational estuarine, coastal and regional models here.
Remember that gridgen is only a tool, and one needs quite a bit of skill to generate a particular grid. It used to take up to two weeks for me to generate a grid for an operational coastal or estuarine model (including testing a few candidates for stability and performance), but it is worth it.
If you are using gridgen you may also need gridutils to work with the grids it produces.
There are a number of front-ends to gridgen. Two of them are octant - a python suite for interactive grid generation for ROMS and GETM - and pygridgen.
Checkout gridgen by running git clone https://github.com/sakov/gridgen-c
or svn checkout https://github.com/sakov/gridgen-c.
Example grid by gridgen:
