Haskell cabal Taxonomy libary contains tools, parsers, datastructures and visualisation for the NCBI (National Center for Biotechnology Information) Taxonomy datasources.
Input data is parsed into a FGL based datastructure, which enables a wealth of processing steps like node distances, retrieval of parent nodes or extraction of subtrees.
Trees can be visualised via dot-format (graphviz)
or via json-format (http://d3js.org/d3js).
The TaxonomyTools package contains tools based on this package.