TrEd
A user-friendly editor/browser with a powerful search engine enables a comfortable human navigation in the data. The visualization captures all the different annotations in a transparent and intelligible way.
btred
Non-interactive scriptable version of the tree editor TrEd. Very useful for automatic data processing.
PML Tree Query
PML Tree Query (PML-TQ) is a query language and search engine that targets querying multi-layer annotated treebanks stored in the PML data format.
Treex
Treex (formerly named TectoMT) is a highly modular, multi-purpose, multi-lingual, easily extendable Natural Language Processing framework.
XSH
XSH is a powerful command-line tool for querying, processing and editing XML documents. It is an interesting alternative to btred.