EventiveEventive is similar to a shoutbox, only, instead of entering a message users enter an event and the script then displays how long is remaining until that event on the page the script is on (designed to be viewed in a iframe),
It is easily customiseable via CSS and displays different messages depenging on whether the event is today, tomorrow, yesterday or sometime in the future.
_http://hotscripts.com/jump.php?listing_id=34420&jump_type=0
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PK CountdownIt allows you to set a certain date and when that date is reached it pops up a message. Planet K used it for a new year countdown and on the 31st of December at 12 oclock GMT is poped up and said "HAPPY NEW YEAR!".
_http://hotscripts.com/jump.php?listing_id=52619&jump_type=0