The following sources (see also: local mirrors of these pages) are consulted daily and used to update the catalog:
Notification of new W3 services should be sent to www-announce@info.cern.ch for inclusion in the W3 Virtual Library and to whats-new@ncsa.uiuc.edu for inclusion in the NCSA What's New list. You can also register services with Aliweb (Archie-Like Indexing for the Web) by filling in this form. New services registered will be will be automatically reflected in this catalog.
Other searchable catalogs can be found on the list of W3 Search Engines and CERN's list of Virtual Libraries. You might also want to consult the local list of W3 FAQs and Guides.
If you want to consult the downloaded source files, look at the W3Catalog directory. If want to make your own copy of this catalog, have a look at the Makefile, and copy the relevant perl scripts, including htgrep. Alternatively, you could simply mirror the entire built-up catalog (large!) and run htgrep locally on the mirrored catalog.
NB: Searches are case-insensitive.