The Mishna at the beginning of Shekalim teaches: on the first of Adar it was announced that the people should prepare their shekalim and check their fields for kilayim - forbidden mixtures; that the Megillah is read on the fifteenth of Adar, and that other services were provided for the community. We are then taught in the same mishna that in Adar the beis din attended to all the public needs. Why does the month of Adar warrant greater attention to servicing the public needs?
The Binyan Shlomo (responsa 55) enlightens us with a novel approach. The Gemorah Shabbos (33b) relates how R' Shimon Bar Yochai and his son miraculously hid from the Romans for twelve years. When he finally emerged, R' Shimon said, "since a miracle was performed on my behalf, I shall go and contribute something to benefit the community." This, we are taught, he learned from Yaakov. When Yaakov arrived (Beraishis 33:18) "shaleim - intact" in terms of his body, wealth, and his Torah, "vayichan es pnai ha'ir - and he encamped before the city". The rabbis understood that he either contributed chain - charm, or changed the face of the city. He either established their own currency, or marketplaces, or bathhouses. In gratitude for Hashem's protection and salvation he showed his appreciation by assisting the community.
Yaakov Avinu and R' Shimon show how it behooves an individual to "pay back" the community upon their personal deliverance. Certainly in the month of Adar when we commemorate our "deliverance from death to life" (Megillah 14a) we should annually direct this thanksgiving and gratitude to some form of communal service and enhancement.
The Gemorah Taanis (22a) teaches us that Eliyahu Hanavi proclaimed that two comedians who cheered up the depressed were destined to go to olam ha-bah. This is further explained by the Maharsha that just as the mishna Sanhedrin (46a) relates that Hashem feels the pain and suffering of the individual that is executed, as one of His children is suffering, how much more so is He pleased when His children are made happy. It is thus understandable that enhancing the welfare of the community brings greater pleasure to Hashem, as "G-d, His Torah, and the people of Israel are inseparable" (Zohar Acharei Mos 23).
Moreover, the entire miracle of Purim evolves around the t'zibur, the community of Israel. Haman charges (Esther 3:8) that the Jewish nation is "mefuzar u'mefurad - scattered and dispersed", lacking unity and concern for one another, and full of strife. To demonstrate the falsity of his charge, "nikhalu ha-Yehudim - the Jews organized themselves in their cities" (Esther 9:2). Again in verses 15 and 18 the theme of the kahal forming one unit is stressed. The very acceptance of Purim by the Jewish nation is expressed by "v'kibail ha-Yehudim - the Jews undertook" (Esther 9:23), written in the singular, explains the Gr"a, to portray their unity.
In addition, the Gemorah Shabbos (88a) teaches the significance of Purim as a time of reacceptance of the Torah. In contrast to the coercion present at Sinai, understood by our rabbis - "vayisyatzvu b'sachtis ha-har - they stood under the mountain" each witnessing gilui Shechinah, (making it almost impossible to refuse Hashem), here at Purim they experienced hester panim - concealment of His presence, reflected by the fact that Hashem's name is not found in the Megillah. As the first acceptance of Torah at Sinai was accomplished in the spirit of "vayichan - they encamped" (Shemos 19:2) at Sinai "as one man, with one mission", similarly at Purim the acceptance was "v'kibail" - as one.
In addition, the mitzvah of mishloach manos is explained by R' Shlomo Alkabetz zt"l (author of l'cha dodi) in his Manos Halevi, that this mitzvah demonstrates the love and brotherhood present in the Jewish nation. It therefore follows that we focus on the needs of the community in this month of national unity.
Perhaps one can further suggest that the response to a miracle is to benefit the community as taught in Shabbos, as an individual should ideally attribute the miracle not to his worthiness, but to the merit of the community. To demonstrate this true humility, he shows his appreciation to the community by his reciprocation on its behalf.
In light of this new dimension and obligation inherent in the month of Adar, might I suggest that each individual, in keeping with "b'chal m'odecha" - serving Hashem with your unique talents and resources, introspect on how you can best serve the needs of, and help fill the voids in, your community. Not only the obvious needs, such as bikur cholim and greater attention to the shut-ins, but also to those needs that might go unnoticed, such as calling the local Yeshiva and offering to tutor a child for free.
Finally, Rav Ephraim Wachsman shlit"a delivered the following inspiring message at the recent siyum hashas in the name of the Tomer D'vorah: all Israel is one collective soul. Your personal learning of Torah is not only a personal fulfillment if talmud Torah, but it elevates the entire community of Israel.