I don't remember how I heard about it but the Making Memories Foundation is a wonderful group whose mission is to "grant wishes, including memory-making events, for metastatic breast cancer patients, while continuing to support, educate and increase resource awareness."
Two sub-groups of the Making Memories Foundation are Brides Against Breast Cancer and The Pink Envelope Project. One of the Brides Against Breast Cancers larger events are their large gown sales used to raise money to grant wishes through the Making Memories Foundation. For more information on these events or to learn more about donating your gown, please visit their homepage at http://www.bridesagainsbreastcancer.org/.
The Pink Envelope project is another great group that encourages brides to host pink envelope bridal showers, or even receptions. There is, of course, no obligation but through the Pink Envelope Project, brides can purchase small envelopes for their guests to make a contribution. For more information, and to learn how to host your own Pink Envelope party, you can register at http://www.pinkenvelopeproject.org/.