I've found my jobs' internal (social) message boards/mailing lists/Slack channels/etc to be great resources as the only contributors are those who work/worked at the company. Your (ex)coworkers presumably met/meet a certain competency bar and are less likely to spam. At larger companies there are message boards/mailing lists/Slack channels/etc for nearly every topic.
For local information, I've found forums for local sport teams to be great resources during the off season. Posters are often happy to engage in any sort of chat during the off season. Even if you haven't gotten to know the frequent posters during the sport's season you can use the (usually highly visible w/o any additional clicks) account age/# of posts/"karma" as a proxy of posters' trustworthiness. note: If you don't normally contribute on-topic (i.e., about the team and sport) posts, I would only search the forums for your questions and not post off-topic questions as that'll get you quickly banned.