HamDB.org is a free amateur radio callbook that offers it's data in four friendly formats (HTML, XML, JSON, & CSV). There is no subscription fee, no account needed, no ads, no session id, and no lookup limits. Just free data in friendly formats.
Our database is updated as quickly as new information is released. Currently Australia, Canada, and the United States call information is updated daily while Germany and the Czech Republic is updated on a monthly basis.
We're always seeking to add more countries to the database. If you know of published amateur radio data for a country we haven't listed, please reach out to us!