The database-type websites include CoinArchives and Tantalus. Some sites such as vcoins have provided links to "pre-formed queries", which look to the web spiders like normal pages. WildWinds "See Also" links have provided some visibility of the spiders into CoinArchives' data, but only the first 100 items for each category (the arbitraty limit set on CoinArchives' queries), and there are a lot more than, say, 100 Nero coins there.
It would be well for designers of relation database type sites to provide pre-formed queries for the spiders to access all the data, and shine a light on all that dark data!