We specified no gifts for our wedding, and if you do too, be prepared for gifts anyway. People want to give you presents for this happy occasion. At our moms' insistance we set up a couple gift registries. Target, Williams Sonoma, and Restoration Hardware. We received a couple items from each place, some gift cards, some cash, and a few items not on our registry (see my cheese lady--it never would have occurred to us to register for it, and we love it!). It was nice that people still wanted to get us something special even though we had said "your present is your presence."
In my mind, registries are a no brainer. Even if you don't want gifts, even if you'd prefer cash, just do it. People will want to get you something. It's nice and you should accept it graciously. Surely you can find a few items at a store that you'd appreciate receiving. Registries aren't just fine china and linens anymore. You can register at places as diverse as Target, Home Depot, and Amazon.com for cool kitchen stuff, electronics, DVDs, and even house paint I guess, if you're registering at Home Depot. You can also register for honeymoons. The possibilities are pretty much endless.
Now I'm going through the process of figuring out which registry items we didn't receive but I'd still like to have. Target and Williams Sonoma both sent 10% discount coupons for buying remaining registry items. And people gave us gift cards to both places. We're trying to put the gift cards toward registry items and for the Target ones, for things we might need for the honeymoon.
Gift registries. Have fun with them! They are nothing to stress out over. Presents = good!