The launch date has been set, but it is still changing, most recently due to the weather in French Guiana, where it is presently scheduled to rocket off planet on Christmas morning.

Briefly, the James Webb Space Telescope is an ambitious plan to site an infrared detector with associated recent tech components at Lagrange point (L2) on the outside of Earth's solar orbit. It will take up to a month to get into position and due to the complexity of the craft and its manifold parts, it will be self-assembling over the next six months.

Step one, getting this very complex and valuable equipment launched, is currently set for 7:20 EST 25 December, but consult the website for updates.

You can find their website, which appears to be very well organized with background and latest schedule updates at: James Webb Space Telescope website