how to include my future sister-in-law

If you are having a mass at the wedding she could bring up the gifts to the altar.

Otherwise maybe she could give a toast at the reception?

How about a toast at the reception?  That's what we've asked my FI's sister to do.

What about having her stand near your guest book to greet people and make sure they sign it?  She could be the "greeter" :).  I'm having my uncle and his wife stand in the foyer by the wish tree to welcome them, explain what the guests are to do witht he wish tree, etc.

or just bite the bullet and ask her to be a birdesmaid (that is what I am doing). FI will be really happy you asked, and she can say no, then you don't have to have her do anything special. I definitely wouldn't put her to work though, like at the guest book. I think that would just make her annoyed with you.

hand out programs?

Maybe you should ask her.  Express that you'd like to include her, but you're not sure what she'd want to do or would be comfortable doing. 

Maybe an usher and/or another greeter @ the sign-in table.

echoing nova here - if you are having a catholic wedding, there are many things she can help with during the offertory.

i agree with nicksnack, if you can - try to see what she'd be comfortable doing. you don't want her to be obliged. HTH.

If you are having flowers girls you can have her walk the aisle with them. This is what I asked my sister in law to do at my wedding. I loved including her. My other two sisters were bridesmaids and my good friend was MOH. Last minute I realized I really wanted my Sister InLaw to be a part of the wedding too..

Hi, I would find some non-demanding way to include her in the ceremony (since she might be quite a distance from you). However, I would caution you to think seriously about including her as a bridesmaid. I did just that and since I don't know them very well, they are not as committed as I had hoped to participating in events and making the wedding process special. Obviously, you have to go with your gut...I thought I did (I thought it was a nice gesture) but I regret it. I think I could have made them feel special without making them bridesmaids and I would be much happier.