Q & A type of sites generally get a lot of traffic which can be channelized to your main websites and increase your revenue. Q & A is a proven business model for many years with successful sites like Stack Overflow, eHow etc.

If you are looking forward to create a how to site, there is s new Q & A Plugin called AnsPress which looks promising.  AnsPress a most advance community question and answer system for WordPress plugin which is still under development, however you can use it & keep an eye on the updates.

Some of the features which will available in version 1.0 are:

• User point system
• Better voting system
• Better admin interface
• User profile
• Choose Best Answer for Question
• Revision control
• Multiple authors
• Point based user access
• Filter questions
• Sort answers by votes and date
• Quick ajax search system
• Ajax based form submit