In general, in most etiquette books, it is considered very bad taste to include a gift registry with the invitation to a wedding (although it has become fairly common practice these days because people just don’t know any better). In some ways it helps people who have no idea what to give the couple a few ideas, but a registry is in no way an obligation.
The shower is a separate event from the wedding. You are not obligated to give a wedding gift, but it would be very nice if you could give them something. A lot of people are down on their luck financially these days, so unless this particular couple is mean and snobby, they will not be offended by a small or token gift, or even just a card.
A few inexpensive ideas that I have given as gifts: a framed photo of the couple that you took. A cookbook that goes along with either of the couple’s ethnic background (I actually found a Jewish/Italian cookbook for one of my friends’s wedding and they were so pleased). A beautiful Sake set (can be found for less than $20 at a Japanese market) or a set of Japanese soup bowls with those big spoons and a set of chopsticks. Or this Book of Us which is a nifty book for couples that ask a lot of interesting questions that the couple may not have known about each other for $10. A brand new address book (they probably both have their own old ratty books, but now that they’re a couple they can combine their addresses and leave out the old outdated stuff). Or a nice photo album for them to fill up with their new life together, for less than $20. Or even a set of plastic picnic dishes from Target or Walmart. They’ve got some really cute inexpensive stuff right now.
Whether or not there is a gift table at the wedding reception depends upon how formal the wedding is. A bunch of my cousins had very informal weddings with a gift table, but the presents were always taken home and not opened in the presence of the guests, to open wedding gifts in front of guests has always been considered bad taste, although with shower gifts that is part of the fun. With more formal weddings, the gifts are usually mailed to the home of the bride and groom.
So go to the wedding and have a good time, give a small token gift or just a card and hope that the couple is decent and loving and not just crass folks looking for a shakedown. You probably already know what kind of folks the couple are and that should guide your decision about whether to go or not, or whether to give a gift or not.