I ran across an article that was geared towards helping people build online libraries of content the natural way! The web page lists out 50 different ways that an internet business owner can do to encourage user interaction on his/her website. The article not only provides tips but also tools & guides that you can refer to along the way.
If you want to use Social Media & Marketing tactics to increase user activity & traffic check out the article, 50 Tips and Resources to Implement User-Generated Content