All around the world, Shri Aurobindo's and the Mother's desciples, devotees and people desiring their grace and blessings celebrate the Siddhi Divas of Shri Aurobindo on November 24 every year, mostly by joycely conducting and particiapting in group mediations and prasad distribution. This is one of the most important Darshan day, on par with darshan days of Aurobindo's and the Mother's birthdays. At Shri Aurobindo Ashram, a large number of devotees visit Shri Aurobindo's room pay their respect and meditate at the Samadhi of Shri Aurobindo and the Mother on this day. Sri Aurobindo himself wrote on several occasions about the significance of Sidhhi Diwas in his own sadhana for supramental realisation and light leading spiritual progress of the world to a new level.
In October 1935 he wrote the following : “The 24th November, 1926, was the descent of Krishna into the physical. Krishna is not the supramental Light. The descent of Krishna would mean the descent of the Overmind Godhead preparing, though not itself actually, the descent of Supermind and Ananda. Krishna is the Anandamaya; he supports the evolution through the overmind leading it towards his Ananda.” Thus "the Delight consciousness in the Overmind which Sri Krishna incarnated -as Avatar- descended on this day into the physical, rendering possible the descent of the Supermind into Matter". (http://nextfuture.aurosociety.org/the-day-of-siddhi).
I too have visited Ashram many a times on this day and participated in all the programmes. These events have been very important in my life's journey. May Shri Aurobindo and the Mother bless us all on this occasion.