I always think jewelry is a smart bridesmaid gift. You know your girls will get use out of it, and it gives you some leeway with your bridesmaids' dresses: You can choose different styles to suit each one's figure best, and then use the jewelry to unify their look.
And let's face it: A bride who makes sure each of her besties gets a pearl necklace on her wedding day is going to be a popular woman for years to come.
I love the bridesmaid collection at Anna Bellagio. It's got everything from simple elegance to extra-sparkly, and there are clever search variables so you can easily find pieces to fit your wedding theme.
...And you just might be able to find something over there for you too.