Chris A. a11n

This plugin requires PHP 5.3 or later, please check with your web host if you’re unsure.
Adoption uses the timezone that is set in the WordPres admin panel. Ensure you have set your local timezone in Settings > General.
Features:
<ul>
<li>Displays a bar chart with registration statistics for predetermined time periods (e.g. this week, last week, last 3 months, last 12 months, etc.)</li>
<li>Displays a “Quick Statistics” section which includes a summary of user registrations for popular time periods.</li>
<li>Easy to use, tidy and fits in with the overall WordPress user interface.</li>
</ul>

Adoption

Adoption displays user registration statistics in a neat dashboard widget

dyerware

This plugin allows you to easily insert charts into your blog, by way of shortcodes. While multipurpose, the chart system is intended to make it easy for posting detailed review measurements of some sort, such as poll data, video card comparisons, sports scores, etc. You specify the names of the devices being measured, the tests performed, and each device’s measurements for said test.
An admin settings page allows you to tailor many shortcode defaults, simplifying overall use.
The shortcode is supported on posts, pages, and in widgets.
Graphs scale to meet the size of the end-user client display, and support mobile displays such as those rendered by the wptouch plugin.
Charts supported are horizontal bar, stacked horizontal bar, vertical bar, stacked vertical bar, line graph, and pie. More can be added if desired.
PHP5 Required.
The shortcode format is:
[easychart argument=”value” …]
For a complete example and more detailed documentation, visit the plugin home page. If you do not understand these instructions, please ask questions in the comments section on the plugin home page. We will be more than happy to answer them.
Go here for up-to-date usage and examples: 
<a href="http://www.dyerware.com/main/products/easy-chart-builder/easy-chart-builder-plugin-for-wordpress.html" title="EasyChart Tutorial" rel="nofollow ugc">EasyChart Tutorial</a>

Easy Chart Builder for WordPress

This plugin allows you to easily create charts within your blog by use of shortcodes.

Adoption vs Easy Chart Builder for WordPress