Check out this website:
I was introduced to this view point in the late 90's by my MIL. She had read "The Sign" by Robert Van Kampen and was doing some serious investigation into the pre-trib rapture view. I read the book (also Pre-Wrath Rapture by Marv Rosenthal) and did my own studies and was convinced. This is very controversial and some people get very angry but it is worth your time to look at it. This is another good site to go to:
Marv Rosenthal is doing an excellent study on Revelation right now and the Zions Hope magazine is wonderful!! Happy reading!