You don't want to leave. These are quite literally the best sites on the net. This is when you find yourself surfing over lunch, and begging someone to go to the corner store for you so you can continue to surf. These are the sites that make you get home late from work, that keep you from your family and force you to eat mountains of fast food because you don't have time to cook. You add things to the site which make people want to come back, day after day, and spend as much time as they can while they are there.
Good content is the key - plus a few bells and whistles.
One thing that many sites can make use of is games and puzzles. All you need to do is find them, add them to your site and watch your visitors have fun. Here is a quick list of a few sites which contains games and puzzles that you can freely take and add to your own pages. A huge and wonderfully fun site is called EncycloZine. This site has a treasure trove of puzzles and games, with links to many different sites containing even more fun stuff.