Tree analysis using New Technology (TNT)
A program for phylogenetic analysis under parsimony (with very fast tree-searching algorithms; Nixon 1999, Cladistics 15: 407–414 doi:10.1111/j.1096-0031.1999.tb00277.x; Goloboff 1999, Cladistics 15: 415–428 doi:10.1111/j.1096-0031.1999.tb00278.x), as well as extensive tree handling and diagnosis capabilities.
As of November 2007, the project was subsidized by the Willi Hennig Society, and thus the program is now freely available, upon agreement on the terms of the License. The license provided is a single-user license, and the most important requirements are that the program is not posted in other websites or mirrors, and that when publishing results you acknowledge having used the Willi Hennig Society edition of TNT and cite the paper describing the program (Goloboff et al. 2008, Cladistics 24: 774–786 doi:10.1111/j.1096-0031.2008.00217.x).
TNT is available for OS-X, Windows, and Linux operating systems.
A thorough Wiki and guide useful for teaching, scripts, branch length, and other information is also online.