While, one can try and meet people in real, it is often not possible for everyone. In such cases, it would be really nice if we had a list of online forums, communities, QA sites for niche/industries where we can interact with potential customers. There many such sites for technology and business (Like HN) but not many for other niches(or I don't know about them if they exist).

Why not make a list/directory of such websites? Submit such websites you know about. I will start with these :

- http://www.t-shirtforums.com/

- http://beta.threadless.com/play/forum/

- http://recordingquestions.com/

- http://www.bodybuilding.com/

- http://lawyrs.net/

- http://www.lawlink.com/

- http://news.knotist.com/

- http://www.meetpips.com/

- http://www.freshpips.com/

- http://ozmosis.com/

- http://www.parentsconnect.com/

- http://www.minti.com/

- http://www.myshutterspace.com/

- http://activerain.com/

- http://www.fohboh.com/

- http://doc2doc.bmj.com/

- http://www.doctorshangout.com/forum

- http://www.accountantforums.com/

- http://forums.foodservice.com/

- http://www.roadfood.com/Forums/

- http://www.restaurant-community.com/

Some general purpose websites where one can find potential customers :

- Quora

- Reddit/Sub-Reddits

- Facebook Groups