"Always a bridesmaid... never a bride?"
I've only been a bridesmaid once... but the stigma still haunts. However, nothing is more honoring than being chosen to stand with a woman. Standing with her, for the commitment they make together, the accountability with those present.
As a MOH you are there to serve, prep, and primp the bride herself, not to mention the obligatory bridal shower. From Bridal Shower Invitations [follow the link for great info & tips on the subject] to Bridal Shower games... you're sure to have your hands full! Just remember: this is her day, bless the socks off of her.