SIMILE Timeplot is the biggest one I know of http://www.simile-widgets.org/timeplot/

We use it in our metrics site. Doesn't look quite as nice as this, and we had to hack in zooming / drag range selection and a few other things.

I'm certainly interested in evaluating replacing it with this.

The biggest thing we have with Timeplot that I don't see here are event markers. On the demo page linked above, if you click on one of those pink areas, you'll get a little popout that you can use to display useful information about a particular event point or range.

Flot isn't really targeted to time series data but it works pretty well in our uses.

Another one that I recently saw (on hacker news) was http://www.highcharts.com/ - but dygraph renders much faster, you can actually watch the highcharts library draw as if it was animated.