Turn it into a prom dress. If you know some young girl in need of a prom dress, you can alter your old bridesmaid dress to fit a teen girl and make a prom dress. Since most bridesmaid dresses are made fashionable whatever the season is, your bridesmaid dress can easily be reused for an occasion like a prom.
Turn it into a cocktail dress. By tweaking your old bridesmaid dress, you can make an all new cocktail dress out of it. You can add some designs and detailing to the dress to create a whole new look.
Know an upcoming bridesmaid? Give it away. This may be the easiest way to bring a whole new life to an old forgotten dress. By giving away your bridesmaid dress to an upcoming bridesmaid you save yourself a new closet space, and you save the other girl money from buying a new one or even renting one.
Make money of it. If you think your bridesmaid dress is still in good condition and the style is still up to date, you can try selling the dress online or to someone that you think may have an interest on it. You can do minor alterations like shortening the length or removing sleeves if this will make the look of the dress trendier.