http://revach.net/article.php?id=3592

Section: Hanhagos   Category: Minhagim
Maos Chitim In Honor Of Avrohom Avinu
Our of all the Yamin Tovim there is a special minhag before Pesach to make sure that the less fortunate have all the provisions needed for Yom Tov.  Why specifically Pesach?

The Minhag Yisroel Torah brings from Rav Yaakov Aharon MiAlexander who quotes his rebbe the Yehudi HaKadosh MiPeshischa, who explains the enigma of why the great tzaddik Avrohom was so concerned that Bnei Yisroel leave Mitzrayim with great wealth.  The reason is that there are two tests a person can face in Avodas Hashem, poverty and wealth.  Wealth is a far greater challenge than poverty.  In Mitzrayim Bnei Yisroel faced the test of poverty, and Avrohom, who wanted them to ascend a higher level, insisted that Hashem bestow on the them the wealth he promised for them to achieve this elevated status.

Therefore since Yetzias Mitzrayim was a transition to the difficult challenge that accompanies great wealth, in order for everyone to participate, we give Maos Chitim to make sure that every Jew has all the adequate means and does not lack anything for the Yom Tov.