Now, this comes from a recent bride - just scan her registry and buy her something really nice/special from that. There is bound to be something. I can't tell you how many pitchers/bowls/wine glasses/etc I got that were lovely, but NOT my taste AND I couldn't return b/c they didn't give me a gift receipt. Also, I put stuff on my registry that I REALLY wnated - so I was super excited to get those gifts!
However, if you really don't want to - I think honey's idea of a gift certificate is good, or some pretty lingerie (I got something in my wedding colors and thought that was great!), or a cookbook of the food they like. Something in that vein that isn't "personal taste" oriented is good.