Question-Answer sites are very helpful to generate genuine traffic for your site. It is one of the methods that I use myself. You just need to spend a minute or two promoting your site in a proper fashion on those question-answer websites, and you can wait and see the traffic flowing in.
What you need to do is, go to these sites and find some questions related to your niche, then answer the question properly giving a link back to your own website. For example, one of my posts talks about Torrific Alternative. So, to promote this particular post on a question-answer website, I look for a similar question that asks for a Torrific alternative or how to direct download torrents.
When I find a similar question, I give a genuine response with a link to the post on my website. That way, I can promote the post and get users who are interested to read it. Sometimes, I do create questions on my own and answer them myself.
It is a promotional strategy but I don't think it is bad in anyway - the question-answer site gets more question and I get more traffic. It's a harmless method. I suggest you people to try it, if you haven't done so already. Remember, it's okay to link to your site but do not Spam the links on every question!
Here are some question-answer sites which you can try to generate traffic :
The best one I have found so far. There were times when I used to get 180 visits daily from a single answer I made there. Both Question and Answers need to be approved by the staffs before it is posted.
Another Question-Answer site that works like a charm. No approval is required to post question and answers.
Answers community with lots of users. If you can promote your site properly here, you can get lots of traffic. Yahoo Answers is very strict though. So do not try to spam or even post the same answer on many questions; they'll get suspicious and ban you immediately.
You can start asking questions and answering them, immediately after you register. You can easily log-in with your Facebook or Twitter account.
5. Aol Answers
Answers community similar to Yahoo Answers. However, they are not strict and you can even post same message or links on many questions without getting banned. Just make sure to post on the appropriate questions.
Here are some other Question-Answer sites to try :