I often go to space-track.org and download the latest space catalog on Resident Space Objects (RSO) and also like to look at the Conjunction Data Messages to check out the probabilities. what other catalogs are out there? I'm assuming Celestrak.com gets most if not all of its information from space-track. Are there other open to the public RSO catalogs out there? there are a lot of commercial ones catalogs, some which require $$, but are they all sourced to space-track? I'm an American and can't even view the EUSST catalog.
The Russian JSC Vimpel Data Portal provides some RSOs that are not part of Space-Track. The delta is mostly debris from some old rocket body break-ups. I am not sure if there is any correlation work to consolidate the Vimpel data with the Space-Track data, I would love to be corrected.
A 3D visualization tool that ingests those is called ASTRIAGraph, built at University of Texas at Austin. You can choose the data source of a few catalogs in that tool from the menu on the left.
The SeeSat-L list of "secret" Space-Track objects is also there. The states of those objects are not updated on a very consistent/fast cadence and is made by the oldest amateur astronomy society to date, but still it may be useful!