Several Religious organizations and even the Knesset in Israel have chosen Taanit Esther as International Agunah Day. The purpose in doing so is to publicize the plight of Agunot, women who are not able to obtain a Get, a religious divorce, from their husbands. There are efforts with the support of some of the preeminent Rabbis in our times to help eliminate this problem. The main vehicle has been the halachic prenuptial agreement, theprenup.org.
There is an organization called ORA, Organization for the Resolution of Agunot, getora.org, that is an incredible resource for these efforts. You may recall that Dovid Halpern (husband of Tamar Halpern, who came to BIAV last year a number times as a Visiting Scholar) interned for ORA and gave a presentation to our community about this topic.
Dr. Rachel Levmore has presented a meaningful connection between the theme of Taanit Esther and praying for the plight of Agunot. In a nutshell, her idea is that Esther suffered in silence until her cries and the prayers of her fellow Jews were effective in reversing the decree against them, and allowing her to go from darkness to light. You can read further in these two links.
http://eng.beithillel.org.il/
http://blogs.timesofisrael.
Let me know if you have any questions!
See also the attached article from YU’s Purim To Go, from Rabbi Jeremy Stern, “Giving Voice to Silenced Women”
http://download.yutorah.org/