Metadata tagging tools are generally add-on products to large CM System software. For example, Documentum Content Intelligence Services automates and controls the attribution and organization of enterprise content based on powerful information extraction, conceptual classification, business analysis, and taxonomy and metadata management capabilities.
And Joseph Busch sold his MetaTagger to Interwoven. Interwoven MetaTagger™ Content Intelligence Server, part of the Interwoven Content Intelligence product family, drives content relevance for critical initiatives like portals, enterprise search, and business applications, enabling organizations to reduce costs, realize higher revenues, and improve workforce productivity.
Some resources for metadata tools.
Some other lists of metadata tools: