This resource was new to me although the site hosting it isn’t. Carl Malamud’s Public.Resource.Org is a well-known source for government documents. I didn’t realize he was also hosting an archive of IRS Form 990s from thousands of U.S. non-profits and other organizations who have to file a return if though they are exempt from paying taxes.
In fact, I couldn’t find it on the main Web site but you can browse the Bulk portion by going directly to the top URL: https://bulk.resource.org/. Some of the other content hasn’t been updated in the last year, although that may reflect the actual government publication schedule. There are U.S. state public safety regulations (administrative codes dealing with things like elevator installation, etc.) and patent and trademark databases. Once you’ve found a directory that has content you’re interested in, consider using a site delimiter in Google to search it. For example, if I want to find Society for the Prevention of Cruelty to Animals (SPCA) groups, I might search Google using: