1. It is acceptable etiquette to register for baby shower gifts and to include where you are registered on the invitation.
2. It is acceptable to register for bridal shower gifts and include the registry on the invitation.
3. It is acceptable to register for wedding gifts, but it is not acceptable to include this information on the invitation.
4. Is it acceptable to register for birthday gifts?
Does anyone have any idea why you can include registry info on some of these things and not on others, because I'm baffled?
Suggestion:
You are not throwing your own shower and the purpose of a shower is to shower the bride with gifts. Therefore stating where she is registered is helpful. The bride and groom throw their own wedding and the point of a wedding is not to give gifts.
It is highly inappropriate to register for baby shower gifts for a 2nd or 3rd child. It is inappropriate to mention gifts in any way when you are inviting someone to an event. It makes a gift feel obligatory when it is not.
As for birthday parties, usually the birthday child makes a list. I don't know that we'd call it a registry as the gatherings are usually quite small. But for smaller gatherings, an invited person would usually call the mother and ask what the child's interests are this year.

{ 4 comments… read them below or add one }
The purpose of a wedding is to celebrate the couple's new life together, not to profit from it. Although it is customary for guests to give gifts (usually money in our culture), it is not necessary nor should it be expected. Many brides have wedding showers given by the bridal party sometime before the actual wedding. This is the time to mention the registry on the invitation as this is the purpose for it.
Just because everyone does something, does not mean it is acceptable, etiquette wise. I know I'm really old-fashioned, but I NEVER include registry info with any type of invitation. I have hosted showers, both bridal and baby, and with each one I provide a number for RSVPing. When people phone to RSVP I take the time to ask if they are interested in registry information. That way the registry is spread by word of mouth, the way it should be.
If you add a gift registry to a wedding invitation, it looks as if you were demanding a gift and as if the invitation were conditional to the gift… highly inappropriate.
The purpose of a shower is to receive gifts, so why not add it?
Michael
So first, let me see if I have this right:
1. It is acceptable etiquette to register for baby shower gifts and to include where you are registered on the invitation – Usually this is done by the person throwing you the shower just to make it less awkward. My sister registered at myregistry.com and they had this feature where you can invite someone to announce your registry for you. Soooooo…she asked me naturally lol.
2. It is acceptable to register for bridal shower gifts and include the registry on the invitation. – I think this turns people off because the invite is a friendly gesture letting your guests know that you want to have them at your wedding and the invite is about them. I wouldn't include registry info in the invite. However, you can definitely announce it afterward and, even more likely, people will ask you where you're registered!
3. It is acceptable to register for wedding gifts, but it is not acceptable to include this information on the invitation. – Yes. Remember, registries are not mandatory but they provide guests with a list of suggestions of items you'd find helpful and/or need. We are getting married and registered at myregistry.com too since I got to know the site after coordinating my sister's baby shower and we added one of those cash gift funds for renovating our home. We included other gifts of course but I think the thing about registries is that they emphasize what you could use and show guests your overall taste (so even if they veer off the registry they'd have an idea of what you like).
4. Is it acceptable to register for birthday gifts? I think so. I don't think it's acceptable to tell everyone and their mother about it because, seriously, it's just a birthday but my little nieces have birthday wish lists (and Christmas ones at that). The lists are small but helpful in knowing what an appropriate gift for them would be and what would excite them. I think it's fine to register for birthday gifts and let your family know about it since usually they are the ones getting you the bigger items! (iPad anyone? lol)
Does anyone have any idea why you can include registry info on some of these things and not on others, because I'm baffled? The etiquette world is so overbearing so I say just never include registry info with an invite and that is the only rule for me. Have fun with it!