[gmx-users] How do you compute drug partial charges?

[nicolis at guideo.fr]

Hello,
We are planning to model drug/metal cation interactions.
What do you use to build your model molecule and to compute partial 
charges to include in the topology file?
Some years ago, I used to use Tripos Sybyl, which included Gasteiger, 
Marsili and Huckel algorithms for partial charge computation.
What are the free alternatives? Any suggestions?
Thank you,
Yiannis