Webmasters: How do you make inactive members active again?

You will eventually run into a problem, your website members will become inactive after a certain time period. What do you do as a webmaster to make your inactive members want to come back? Do you offer specials, or promotions? Do you beg them to come back via email? Do you offer them the world to visit the site, and see if they would like to login again? Is your method very creative or just a simple email?

So what is it exactly that you do to ensure those inactive members come back? You can not run a dead website, that'll be boring!