Building and Maintaining Large, Collaborative Databases?

hherb asks: "We are in the process of building and maintaining a free pharmaceutical reference database, in order to liberate medical decision support systems from vendor driven databases. For that purpose, we need some way of allowing multiple authors to contribute to a large number of data records - most of them small...too small for CVS. We need version tracking as well as authentication of authors. We need to tag every bit of information enterrred with information about source reference, author, peer review result, and so forth. I had a look at existing version tracking software. like CVS and Subversion, and I did not have the impression that any of them would suit our needs. Does anyone have ideas for *free* software solutions that we can use?"