Regular registration for the National Military Family Association's wonderful Operation Purple camps ended last Friday, April 16, 2010. However, registration has been extended for certain locations.
When you first look at the site, it seems as if the registration has been extended for every location. However, if you click on a particular camp, there will be a block at the upper right of the page (right under the location name) that either says "Register Now!" or "Camp registration has closed." There doesn't seem to be a way to sort by just the camps that are still accepting registrations.
The registration deadline has only been extended until April 26th, so don't wait!