At 7am PST today, the campsite reservations for Yosemite Valley opened up for mid-June to mid-July. While I was hitting the website, both my wife and I were calling in the reservation number and could not get through either way.
When we finally got through on the phone 13 minutes later, all the sites for our target date of July 5 were gone along with the rest of the month.
Luckily, I saw that you could start a reservation on July 14 (last day of this open period) and have it extend into the next period. With only 12 sites in the Valley that will hold a 40 ft rig, I was able to reserve a site in the North Pines campground for 7 nights. Fortuneately, we had some flexibility in our schedule.
Our son may be working as a chef in the Ahwanhee Hotel this summer, so we really wanted to stay in the Valley and see him during his rare, off hours. So it was a VERY stressful 13 minutes!