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