01. Dygraphs

Dygraphs is a fast, flexible open source JavaScript charting library that allows users to explore and interpret dense data sets. It's highly customizable, works in all major browsers, and you can even pinch to zoom on mobile and tablet devices.

02. ZingChart

03. InstantAtlas

If you're looking for a data viz tool with mapping, InstantAtlas is worth checking out. This tool enables you to create highly-interactive dynamic and profile reports that combine statistics and map data to create engaging data visualizations.

04. Timeline

Timeline is a fantastic widget which renders a beautiful interactive timeline that responds to the user's mouse, making it easy to create advanced timelines that convey a lot of information in a compressed space.

Each element can be clicked to reveal more in-depth information, making this a great way to give a big-picture view while still providing full detail.

05. Exhibit

Developed by MIT, and fully open-source, Exhibit makes it easy to create interactive maps, and other data-based visualizations that are orientated towards teaching or static/historical based data sets, such as flags pinned to countries, or birth-places of famous people.

06. Modest Maps

Modest Maps is a lightweight, simple mapping tool for web designers that makes it easy to integrate and develop interactive maps within your site, using them as a data visualization tool.

The API is easy to get to grips with, and offers a useful number of hooks for adding your own interaction code, making it a good choice for designers looking to fully customise their user's experience to match their website or web app. The basic library can also be extended with additional plugins, adding to its core functionality and offering some very useful data integration options.

07. Leaflet

Another mapping tool, Leaflet makes it easy to use OpenStreetMap data and integrate fully interactive data visualisation in an HTML5/CSS3 wrapper.

The core library itself is very small, but there are a wide range of plugins available that extend the functionality with specialist functionality such as animated markers, masks and heatmaps. Perfect for any project where you need to show data overlaid on a geographical projection (including unusual projections!).

08. WolframAlpha

Billed as a "computational knowledge engine", the Google rival WolframAlpha is really good at intelligently displaying charts in response to data queries without the need for any configuration. If you're using publically available data, this offers a simple widget builder to make it really simple to get visualizations on your site.

09. Visual.ly

Visual.ly is a combined gallery and infographic generation tool. It offers a simple toolset for building stunning data representations, as well as a platform to share your creations. This goes beyond pure data visualisation, but if you want to create something that stands on its own, it's a fantastic resource and an info-junkie's dream come true!

10. Visualize Free

Visualize Free is a hosted tool that allows you to use publicly available datasets, or upload your own, and build interactive visualizations to illustrate the data. The visualizations go well beyond simple charts, and the service is completely free plus while development work requires Flash, output can be done through HTML5.

11. Better World Flux

Orientated towards making positive change to the world, Better World Flux has some lovely visualizations of some pretty depressing data. It would be very useful, for example, if you were writing an article about world poverty, child undernourishment or access to clean water. This tool doesn't allow you to upload your own data, but does offer a rich interactive output.

12. FusionCharts

FusionCharts Suite XT brings you 90+ charts and gauges, 965 data-driven maps, and ready-made business dashboards and demos. FusionCharts comes with extensive JavaScript API that makes it easy to integrate it with any AJAX application or JavaScript framework. These charts, maps and dashboards are highly interactive, customizable and work across all devices and platforms. They also have a comparison of the top JavaScript charting libraries which is worth checking out.

13. jqPlot

Another jQuery plugin, jqPlot is a nice solution for line and point charts. It comes with a few nice additional features such as the ability to generate trend lines automatically, and interactive points that can be adjusted by the website visitor, updating the dataset accordingly.

14. Dipity

Dipity allows you to create rich interactive timelines and embed them on your website. It offers a free version and a premium product, with the usual restrictions and limitations present. The timelines it outputs are beautiful and fully customisable, and are very easy to embed directly into your page.

15. Many Eyes

Developed by IBM, Many Eyes allows you to quickly build visualizations from publically available or uploaded data sets, and features a wide range of analysis types including the ability to scan text for keyword density and saturation. This is another great example of a big company supporting research and sharing the results openly.

16. D3.js

D3.js is a JavaScript library that uses HTML, SVG, and CSS to render some amazing diagrams and charts from a variety of data sources. This library, more than most, is capable of some seriously advanced visualizations with complex data sets. It's open source, and uses web standards so is very accessible. It also includes some fantastic user interaction support.

17. JavaScript InfoVis Toolkit

A fantastic library written by Nicolas Belmonte, the JavaScript InfoVis Toolkit includes a modular structure, allowing you to only force visitors to download what's absolutely necessary to display your chosen data visualizations. This library has a number of unique styles and swish animation effects, and is free to use (although donations are encouraged).

18. jpGraph

If you need to generate charts and graphs server-side, jpGraph offers a PHP-based solution with a wide range of chart types. It's free for non-commercial use, and features extensive documentation. By rendering on the server, this is guaranteed to provide a consistent visual output, albeit at the expense of interactivity and accessibility.

19. Highcharts

Highcharts is a JavaScript charting library with a huge range of chart options available. The output is rendered using SVG in modern browsers and VML in Internet Explorer. The charts are beautifully animated into view automatically, and the framework also supports live data streams. It's free to download and use non-commercially (and licensable for commercial use). You can also play with the extensive demos using JSFiddle.