Wikipedia: Rapture - History and summary of various viewpoints. - http://en.wikipedia.org/wiki/Rapture
The Midweek Rapture - Espouses three future appearances of Jesus, distinguishing the second coming and the gathering of believers, with a mid-tribulation rapture. - http://www.themidweekrapture.com/
Rapture Research Website - Study all the various rapture viewpoints in relation to bible prophecy. Many articles, links and a forum. - http://www.pretribulationrapture.com