This type of listing must be concise. Clearinghouse participants serving from their own site may serve metadata, data and graphics, but must serve metadata conforming to the FGDC's Content Standards for Digital Geospatial Metadata at a minimum. If a server has the actual data available, it should be linked from the metadata so a browser who wants the data sees the metadata first. No restrictions on data format exist. Some agencies have sample data files which users can download to get an idea of the format, size, content and quality of the data.
Some agencies serve the actual data free of charge.
At a minimum, contact information to get cost information is available.