Bluff: Beautiful graphs in JavaScript
bluff.jcoglan.com
bluff.jcoglan.com
http://developer.yahoo.com/yui/charts/
http://www.liquidx.net/plotkit/
ESJChart is really feature complete, but bloated and has a bad interface.
I would try Flot first, and if it doesn't meet your needs try the YUI one.
There's a weird label positioning issue (label text stays a fixed width from the left edge of the screen, not the left edge of the chart) with Google Chrome, but not with Windows Safari or Opera.