Where can I browse common schemas?

Question

It is hackish and myopic to write a new XML schema for a common data situation without considering existing standard schemas. It would be silly, for instance, to write a schema for recording internet bookmarks without considering XBEL.

Yet while a quick search yeilds hundreds of examples of how to write your own DTD, RNC, XSD, etc, I haven't seen a site where you can browse hundreds of standard schemas for particular problem spaces, e.g. product catalogs for e-commerce, office inventories, or lesson plans for teachers.

Where can I browse often-used schemas?

EDIT: This question was originally about where to browse standard DTDs. Then it came to my attention that DTDs are dead - I've now changed my request from 'DTD' to 'schema', which I take to mean a "validatable specification for an XML-based markup language"

EDIT: Links like these, only more comprehensive: 1. Wikipedia's list of Schemas 2. Altova's Schema Library 3. Liquid Technologies' XML Standards Library

Answer 1

Is http://www.xml.com/pub/rg/DTD_Repositories > the sort of thing you're after? I suspect existing standardization is less than you hope.

ALSO, I personally prefer RNC or at least XSD or another rich schema approach whenever possible, in preference to DTD.