how to select all class except the clicked element in JQuery?

Use the not selector.

Example:

$('.collapsiblock').click(function(){
     $('.collapsiblock').not(this).each(function(){
         $(this).slideUp();
     });
     $(this).slideDown();
})

Try this,This is a better way because if you use each function it will load and in the future when you have more than a thousand div it will take a long time to slide up and slide down.

Example:

$('.collapsiblock').click(function(){
   $('.collapsiblock').not(this).slideUp();
   $(this).slideDown();
});