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A comprehensive list of tools is kept by Digital Research Tools.
Webservice that tags your resources
This webservice helps you in tagging textual content both on and off the web. tagthe.net returns a set of tags based on the textual content you specify.
This tool helps you with Terminology Extraction by comparing the frequency of words in a text or document with their frequency in the English language. Words which appear very frequently in the document but rarely in the language are probably terms.
Termine Web Demonstrator
TerMine is the terminological management system containing C-Value term extraction and AcroMine acronym recognition. This tool is ideal for medical texts.
C-value is a method for Automatic Term Recognition (ATR) which combines linguistic and statistical analyses, emphasis being placed on the statistical part.
AcroMine is an acronym dictionary automatically constructed from MEDLINE and contains 886,755 acronyms.
The Wikify! system will analyze an uploaded text or html file and turn automatically selected keywords into Wikipedia-style links.
This is a free software project to enable easy term extraction through a web service.
N-Gram Phrase Extractor
This program will extract word strings (n-grams) up to and including the length you specify.
Beautiful Word Clouds
Wordle generates “word clouds” from text that you provide.
Whatizit allows you to do textmining tasks online. Whatizit is also a Medline abstracts retrieval/search engine. Whatizit is great at identifying molecular biology terms and linking them to publicly available databases.
Reveal Your Texts
Voyeur analyzes the frequency with which words appear in the text you supply.
Make your own tag cloud from any text
TagCrowd is a web application for visualizing word frequencies in any text by creating a word, text or tag cloud.