Build a simple, interactive, historical timeline with HTML, CSS, and jQuery. The benefits of this timeline script are that it's fully accessible and simple, able to handle nearly any form of content, and printer friendly.
jQuery Countdown is a really cool plugin that has a great animation.
Timeago is a jQuery plugin that makes it easy to support automatically updating fuzzy timestamps (e.g. "4 minutes ago" or "about 1 day ago").
jDigiClock is a jQuery plugin inspired from HTC Hero Clock Widget.
FullCalendar is a jQuery plugin that provides a full-sized, drag & drop calendar like the one below. It uses AJAX to fetch events on-the-fly for each month and is easily configured to use your own feed format (an extension is provided for Google Calendar). It is visually customizable and exposes hooks for user-triggered events (like clicking or dragging an event)