Everybody today is talking about social media - Facebook, Twitter, etc. but you can also bring some of those elements onto your own website - no matter what you do, and see an increase in traffic and keep more people interested in your website.
The first thing you should consider in making your website more social media friendly is to integrate it with the other social media websites that are out there. Many websites today, for example, are allowing visitors to log in with Facebook, adding 'like' buttons to their web pages or even allowing visitors to send comments from their site through to Facebook. All of these are great ways to make your website more appealing to visitors and as they get involved on your website and link your website with Facebook so more of their friends will visit you as well.
Commenting has been around since blogs first came out a few years ago and has now gained even more popularity due to social media. You should also consider adding comment boxes to articles on your website as well as your blog and any other pages that you feel people may be interested in sharing on.
Do you have a membership site? Do you allow people to create their social profile on your website? This makes the site more interesting for them and also allows them to connect with other people who have similar interests either for networking or social purposes.
The key with social media websites is communication, lots of it and in a variety of different ways - commenting, sending messages, chatting, etc. A few years back people were promoting starting up your own webmail website where people could check their email from your website in order to keep them there longer; today you needn't worry about webmail but should open up a variety of different ways for people to communicate on your website - both with you and with other visitors to your website.
The more socially interactive your website is, the more people will want to return and the more they return, the more likely they will be to purchase your products and services. Integrating your website with other social media websites also enables you to get more traffic from them. Design your website in such a way that promotes interaction and integrates with existing social networks.