I a searching for QnA sites which help me to make a good quality links, suggest me the name of sites?
Answers.com and Yahoo! Answers might be helpful. The list from @alex06295 looks like it offers a lot of great possibilities.
Try Quora most people post they questions here. It covers a wide variety of topics and interests, and is bound to have something for your curiosity. You can also choose to search for answers to specific questions right in the search bar on every page
thanks for this useful list. Can we make our backlink in these sites easily or we need to go through some ground rule, before dropping any url.