If you're not ready to trash the dress, consider donating your gown to charity. Donated dresses are sold at discounts, and all proceeds go to charity. This is win-win-win all over--you've found a positive way to clean some space in your closet, someone else gets a dream dress they can afford, and a charity gets some financial support.
If you're interested, here are two causes to check out:
Brides Against Breast Cancer
Sheltering Arms' Bridal Garden