Here are some sites I use in my research:
OpenCorporates bills itself as “the largest open database of companies in the world”. It’s a great place to get started. You can search for people or for companies in dozens of jurisdictions around the world (including US states). They also link to the original source material (though sometimes the link ends up being dead).
OpenGazettes gathers data from the official public notices of countries like France, UK, Switzerland, and so on.
For more Gazette notices (and more), check out OCCRP’s Investigative Dashboard
You can see official filings from UK companies on Companies House’s website here. The papers only go back so far, though. And the site is purged after a company has been shut down for some amount of time. Also, remember that people lie and the information in the paperwork is not always accurate (fake / multiple addresses, multiple birthdays, multiple versions of a persons name, etc.). Another way to search in the UK (by postcode too) is with endole.co.uk
I have honestly not found much in the ICIJ’s offshoreleaks that was useful. It has mostly only confirmed information I had already found elsewhere.
Other suggestions (these may sound a bit obvious, but I think they are worth sharing anyway):
- Google the company or individual’s name;
- Google the address of the company or individual you are searching for;
- Google their phone number;
- LinkedIn is your friend;
- So is Facebook;
I’ll keep adding resources here as I think of them.