This online tool can be used for a wide variety of annotation tasks, including visualization and collaboration.

brat is designed in particular for structured annotation, where the notes are not freeform text but have a fixed form that can be automatically processed and "interpreted" by a computer. brat also supports the annotation of n-ary associations that can link together any number of other annotations participating in specific roles. brat also implements a number of features relying on natural language processing techniques to support human annotation efforts.

MMax2 is a text annotation tool for creating and visualizing annotations. It has advanced and customizable methods for information and relation visualization.
Features:

• Determination of the word class / part of speech (POS) for words in a text
• Determination of word senses, including the disambiguation of homonymous and polysemous words
• Detection of anaphoric expressions and identification of their antecedents

The Stanford Part-of-Speech Tagger includes English, Arabic, Chinese, and German tagger modules.

VARD 2 is an interactive piece of software produced in Java designed to assist users of historical corpora in dealing with spelling variation, particularly in Early Modern English texts. The tool is intended to be a pre-processor to other corpus linguistic methods such as keyword analysis, collocations and annotation (e.g. POS and semantic tagging), the aim being to improve the accuracy of these tools.