I maintain a fork of flot on github. The graphs function correctly in IE (barring some here-and-there bugs which you can report). The only issue is speed (always an issue with IE), and as a result I wouldn't try too much of the interactivity... But on the whole it works great.
Can anyone here speak to whether that is a problem or not?
Alternatively, does anybody have a different favorite charting library they'd care to mention?