I thought I should mention a lot of the work Tim Vandermeersch has
done in the current Open Babel trunk on force fields and coordinate
generation.
In a few minutes, I’ll commit the changes that will give initial MM2
and Ghemical/Tripos force field optimization in Open Babel using
steepest descent. This is independent of the libghemical code. The
latter may have better optimization routines at the moment, but
there’s now a framework for doing this in Open Babel itself. (We also
have permission to use a variety of other force fields.)
So the next priority is probably getting some editing tools in place,
but it looks like the other big piece of Ghemical (i.e., simple
molecular mechanics optimization) is ready for Avogadro. 
Cheers,
-Geoff