New version of Flot is out. See the changes.
The date/time support has finalled arrived and there's support for coloring background areas. For instance, you might use this to plot the visitors to the Flot homepage. There's also support for segmented lines. Plus a long list of bug fixes and tweaks.
For the next release, I'll probably be focusing on adding more interactive features. There are some patches floating on the mailing list I need to take a look at.