I start this "list" with a single entry, in the hopes others will contribute to help newbies. Please provide a valid link and any important details. If there were logs exposed, I will mark them in red to alert others that action may be needed.
The next post will contain the list.
UFO VPN - they have a strict "no logs" policy but all their logs were exposed and indexed on a search engine.
IF YOU USED THIS VPN, CHANGE ANY SIMILAR PASSWORDS.