Our family has been celebrating the last day of Pesach with a festive meal called Messiah's meal that we invite friends and family to join us in this celebration. Most of our friends know we are Chassidic in traditions and lifestyle. It is our perferred expression of Judaism. So I will attempt to explain with help from my favorite sources to explain this tradition.
The Last day of Pesach is celebrated by eating a special festival Banquet called Mashiach Seudah a custom initiated by the Baal Shem Tov. The connection of the last day of Pesach and Mashiach is explained by the Tzemach Tzedek. "The last day of Pesach is a conclusion of that which began on the first night of Pesach. The first night of Pesach is our festival comemorating our redemption from Egypt by The Holy One Blessed be He. It is the first redemption carried out through Moshe Rabbeinu who was the first redeemer,it was the beginning. The last day of Pesach is our festival comemorating the final redemption to come, When The Holy One Blessed be He, will redeem us from the last exile through the Righteous Mashiach who is the final redeemer. The first day of Pesach is Mashe Rabbeinu's festival, the last day is Mashiach's festival."
May you all have a wonderful and joyous last day of Pesach!