In the classic web forum sense? Culture and all? I haven't been able to find any (but also I haven't looked very hard in the last 2-3 years). How are you finding out, just word of mouth?
Classic, yes. Forums like XDA-Developers, EEVBlog, Head-Fi, or DIYAudio.com. You can pretty much just search for "<topic> forum" and find them. Many of the best forums in the modern Internet are Russian and Chinese by the way.
Culture is what gives value to a web forum. If it's just an exchange of ideas it gets bogged down with astroturfing