The Tree Set Visualization package is capable of summarizing large sets of phylogenetic trees. It depicts a "tree space" using multi-dimensional scaling based on tree-to-tree distance metrics.
To install in Mesquite (version 2.72 or later), start Mesquite. From the File menu, select Check Now for Notices/Installs, and enter http://mesquiteproject.org/packages/tsv/install.xml.
To install TSV manually, the class files are in these archives: http://mesquiteproject.org/packages/tsv/treeSetViz.zip and http://mesquiteproject.org/packages/tsv/consensusTSV.zip
See the Tree Set Visualization web page.
Source code is available at http://svn.mesquiteproject.org:8080/repository/treesetviz/trunk/