INEX: Initiative for Evaluation of XML Retrieval is another must-see for serious topic map researchers.
No surprise that my first stop was the iNEX Publications page with proceedings from 2002-date.
However, INEX offers an opportunity for evaluation of topic maps in the context of other solutions, providing that one or more of us participate in the initiative.
If you or your institution decided to participate, please let others in the community know. I for one would like to join such an effort.