Matthew 24:37-44:
"But as the days of Noe were, so shall also the coming of the Son of man be.  For as in the days that were before the flood they were eating and drinking, marrying and giving in marriage, until the day that Noe entered into the ark, and knew not until the flood came, and took them all away; so shall also the coming of the Son of man be.  Then shall two be in the field; the one shall be taken, and the other left.  Two women shall be grinding at the mill; the one shall be taken, and the other left.  Watch therefore: for ye know not what hour your Lord doth come. But know this, that if the goodman of the house had known in what watch the thief would come, he would have watched, and would not have suffered his house to be broken up.   Therefore be ye also ready: for in such an hour as ye think not the Son of man cometh." 

Matthew 25:13:
"Watch therefore, for ye know neither the day nor the hour wherein the Son of man cometh."

1 Thess. 4:15-17:
"For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent them which are asleep.  For the Lord himself shall descend from heaven with a shout, with the voice of the Archangel and with the trump of God; and the dead in Christ shall rise first; then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air, and so shall we ever be with the Lord."

1 Cor. 15:51-53:
"Behold, I show you a mystery; We shall not all sleep, but we shall all be changed, In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.  For this corruptible must put on incorruption, and this mortal must put on immortality."

Revelation 16:15:
"Behold, I come as a thief. Blessd is he that watcheth, and keepeth his garments, lest he walk naked, and they see his shame."

Note: Many verses pretain to the upcoming Rapture. These are one's that are most commonly referenced