TreeView X

TreeView X is an open source program to display phylogenetic trees on Linux, Unix, Mac OS X, and Windows platforms.

It can read and display NEXUS and Newick format tree files (such as those output by PAUP*, ClustalX, TREE-PUZZLE, and other programs). It has a subset of the functionality of the version of TreeView available for the Mac Classic and Windows (it is roughly equivalent to version 0.95 of TreeView).