Free term extractors

Terminology extraction tools or terminology extractors can help suggest possible terms for inclusion in translation glossaries.  Term extractors may automatically suggest lists of glossary candidate words and phrases based on a number of factors including repetition, uniqueness, and clustering with other words.
Some term extractors are free.
Free Term Extractors Online

• fivefilters.org
• maui-indexer (downloadable too)
• TerMine (downloadable too)
• AlchemyAPI keyword / terminology extraction

Free Term Extractors for Download (APIs, Code, and Desktop Versions)

• Wordfast (part of PlusTools 4)
• KEA
• topia.termextract
• Araya Bilingual Term Extraction Tool
• Terminology Extraction by Translated Labs

Many of these tools, like ExtractKeyword.com or SEOKeywordAnalysis.com, were originally developed to aid in SEO keyword identification or indexing, but they can still be helpful to translators.

• Five Filters Term Extraction, a free software term extraction service web application
• AlchemyAPI, a web-based multi-lingual keyword / terminology extraction API web application
• Zemanta API, a web-based keyword extraction and disambiguation API by Zemanta
• Yahoo Term Extraction API web application
• Introduction to terminology management, by IBm
• TermExtractor, a free terminology extraction web application
• TermFinder, free online terminology extractor web application
• TrM Extractor, experimental terminology extractor web application that can process English and Hungarian texts
• Statistical Bilingual Terminology Extractor, online terminology extractor web application
• Ngram Statistics Package, open source package for identifying collocations
• Bilingual Terminology Extraction from Translation Memory files, by Masterin, online and free, supports English, Swedish and Finnish (all language pairs and translation directions) web application
• Heartsome Araya Bilingual Terminology Extractor for TMX files, by Heartsome Europe
• English Phrases Extractor, by the Blogscope team at the University of Toronto, extracted terms are used to search for conceptually related blogs over the web rather than for linguistic analysis purpose web application
• A demo of Document Skimming and Scanning using domain-related terms extracted from news articles. The domain terms are organised into 'term clouds' for visualising key concepts in the news.
• An interface for extracting domain-relevant terms from documents using the OT and TH measures. A list of documents together with their automatically-extracted domain-relevant terms are available for browsing here.
• Gabor Melli's info page on terminology extraction
• Yahoo! Quest demo exploiting term extraction for browsing the Yahoo! Answers Q&A collection
• ExtractKeyword, A Free Online Keyword Tool to Extract Keywords, Analyse Keyword Density from Webpages and Paragraphs. Support Vietnamese and English contents.