Tagthe.net

"tagthe.net then returns a set of tags based on the textual content you specified. The service is mainly designed for developers, building applications that make use of tagging."

http://www.tagthe.net/

E.g. put in


http://aroencyclopaedia.org/shared/text/s/semde_ar_eng.php

And obtain

Yeshé Tantra century ngöndro vehicle practice practitioner nature Tantric Dzogchen

dagger - a command line tagging tool

"dagger is a small command-line utility for unix/linux written in Python which tags and renames audio-files. Currently supported formats are MP3 and OGG Vorbis. dagger's configuration file supports different profiles with their own sets of option"

http://www.freewarepoint.de/dagger/

Jiglu: Tags that think

" Jiglu is a super-smart engine that pieces your site together, intelligently tagging and linking your web content"

This is interesting. Embed the widget in your blog and it indexes the content ...

http://www.jiglu.com/