TermExtractor is a software package for Terminology Extraction. The software helps a web community to extract and validate relevant domain terms in their interest domain, by submitting an archive of domain-related documents in any format.

TermExtractor extracts terminology consensually
referred in a specific application domain. The software takes as input a corpus of domain documents, parses the documents, and extracts a list of “syntactically plausible” terms (e.g. compounds, adjective-nouns, etc.).
Documents parsing assigns a greater importance
to terms with text layouts (title, bold, italic,
underlined, etc.). Two entropy-based measures, called
Domain Relevance and Domain Consensus, are then used.
Domain Consensus is used to select only the terms
which are consensually referred throughout the corpus
documents. Domain Relevance to select only the terms
which are relevant to the domain of interest, Domain
Relevance is computed with reference to a set of
contrastive terminologies from different domains.
Finally, extracted terms are further filtered using
Lexical Cohesion, that measures the degree of
association of all the words in a terminological
string. Accept files formats are: txt, pdf, ps, dvi,
tex, doc, rtf, ppt, xls, xml, html/htm, chm, wpd and
also zip archives.

http://www.kinlan.co.uk/AjaxExperiments/AjaxTag2

I also use the Search API, Flicr and Amazon API’s too. :)