It's April 16th, but for those of you still on waitlists with no other offers, I wouldn't give up completely. Looking at gradcafe, it seems a good chunk of folks made their decisions yesterday, sometimes by the end of day. So schools may be contacting waitlisters today or even through next week.
That said, if you know it is the end of the line for you, I would let yourself regroup, maybe lick your wounds for a bit, and then do something fun or worthwhile completely unrelated to grad school. Remember all the other reasons why your life is good and other things you have accomplished or can do well. Maybe even make a list of why not going to grad school this year is a good thing. Then when you are ready, take a deep breath and decide if this is really what you want and what you are meant to do. Is there something else you want more? Should you shift the dream a little? If it is, roll up your sleeves and dive in. Make use of this board and the folks on it, real life friends and colleagues, the Insiders Guide, conferences, and the web. Do your research, realizing you are WAY ahead of the game and the first time applicants for next year. If you want this, no one can stop you. Good luck!
"The greatest glory in living lies not in never failing, but in rising every time we fail."
Nelson Mandela