Originally, Iridium-5 was supposed to be launched by SpaceX on their Falcon 9 rocket on March 29th at 7:19am PST, but has been pushed back a couple days. Matt Desch, CEO of Iridium, tweeted that they are having an issue with one of the ten satellites being launched and are resetting the date to NET March 31st at 7:08am PST (10:08am EST). There is a possibility that the launch could slip into next week, but as of right now 3/31 is the targeted date. "Launch success is priority #1!" Desch tweeted.
Edit: They are now targeting the launch for March 30th at 7:14am PST (10:14am EST)
Iridium-5 will launch on SpaceX's Falcon 9 rocket using a flight-proven first stage which is not planned to be recovered. A new article will come out with more info as the launch grows near.