Check out the demo Timeline of the JFK assasination:

I searched high and low and a was unable to find a competing solution that comes close to SIMILE Widgets’ Timeline.  To my knowledge nothing comes close.  Additionally, a independently developed supporting library aptly named TimeMap uses Google, OpenLayers, and Bing in coordination with the SIMILE Timeline library to load one or more datasets in JSON, KML, or GeoRSS onto both a map and a timeline simultaneously.  You can check out the project Timeline library here and the Timemap project on google code here.

D3.js

The makers of D3.js (previously Protovis) have created an elegant library enabling the developer to bind data to a Document Object Model, and then apply data-driven transformations.  This type of functionality that will become native with HTML5 and the Canvas object and D3.js is poised for the transition with this powerful set of libraries.

D3 Choropleth:

D3 TreeMap:

JavaScript InfoVis Toolkit

Equally compelling and comparible to D3.js is the InfoVis Toolkit.  Created by Nicolas Garcia Belmonte, InfoVis is standards based, fast, beautiful and interactive.  Similarly to D3.js, InfoVis allows you to create a canvas and bind data as objects while providing a powerful library for interactivity.

InfoVis Pie Chart:

InfoVis SunBurst:

InfoVis TreeMap:

HighCharts

Highcharts is a charting library written in pure JavaScript.  Straightforward and intuitive, they currently support line, spline, area, areaspline, column, bar, pie and scatter chart types.  They are perfect for traditional chart types that seamlessly integrating interactive and real time features.  HighCharts has a sister library especially for stock market data called HighStock.

Ajax loaded data with clickable points. If you are familiar with Google Analytics Charts, you will recognize this one. 

HighCharts Pie Chart:

HighCharts Combo Chart:

Dygraphs

dygraphs is an open source JavaScript library that produces produces interactive, zoomable charts of time series. It is designed to display dense data sets and enable users to explore and interpret them.

Comparing two datasets:

U2MRWT3FRYX6

TypeTester

FontTester

A complimentary site that will help you with your style type-storming is TypeChart.  Browse through existing css styles and fonts to get the creative juices flowing, then copy your selection into Typetester and FontTester to refine your styles and make them your own.

TypeChart