Solutoire took part of PlotKit and wrote some parts himself, then made Plotr which does not need the Mochikit library to work with. It is also a lightweight charting framework with only 12kb. There are more than 30 options for you to customize the chart. Like PlotKit, you can display Pie Charts, Line Charts and Bar/Column Charts.

Requirements: Firefox 1.5+, Safari 2.0+, Opera 9.0+, IE6+ (emulated)
Demo: http://www.solutoire.com/plotr
License: BSD License