Here is another off the cuff idea to help your networks succeed. We know contests can really engage your members, such as "Best Photo" "Funniest Video" or "Add-A-Caption", but I've never seen anyone suggest this idea......
A SCAVENGER HUNT! Here is my quick take on an idea. Randomly hide something, say, a picture on your network (best if it fits your niche so it doesn't stand out. For example, Brian K. of Cakes We Bake wouldn't want to hide a picture of a hammer on his site, too easy to notice), and then give a daily clue of what to look for. do this for a time period (say every week) or until someone gets it. I personally would do it every week, to keep people engaged. Say your prize was a 25.00 gift card, and no one got it, after the week (say from Sunday to Saturday) disclose the answer, start a new one, and roll the unwon prize into the next week's hunt! this could seriously increase page views for most any site, but very active ones would be GREAT to keep engagement going. As they look for the hunted item, they may come across content they want to comment on or share. I'd love to hear some other people's ideas on how to run these, too, so share your ideas! Hope you like it, if you use it, let us know how it worked!