What is a good Christmas gift idea for my mother to symbolize her becoming a first time grandmother?

I think an amazing idea would be to go to the local mall and get a Christmas tree ornament personalized with "My first Christmas as a Grandmother - 2009"   Do something that she would not know right away.  She would simply open the box and think it was an ornament.  Then, after she read what the ball said, it would be a complete surprise.  You can have so much fun with this.  Whatever you do, remember that she is going to be excited!

Merry Christmas!!  and Congratulations!!

My mom is becoming a first time grandmother too!  It's a shock to her how fast time is moving, but it will truly be worth it in the end. :)  Anyways, I was thinking of getting my mom a nice, elegant piece of jewelry, possibly turquoise.  I wouldn't recommend one of those necklaces with daughters and sons on them with the symbolical charms.  Those are slightly tacky :)  Best of Luck!

Wow! That is such an amazing moment in one's life! I know when I had my daughter, my Mother fell head over heels and would still go to the end of the Universe for her. (Kinda makes me wonder who this impostor is, since she is clearly not the woman I grew up with) : )
Here are some of the top rated gifts received by first time Grandmothers:

Grandmother's Book of Promises. "One of the richest, most precious relationships a child has is with his or her grandmother. Kids know that grandmas are fun, they give the best hugs, and they make yummy treats! And now, Grandmother's Book of Promises gives boys and girls even more exciting reasons to look forward to special times with Grandma!
Best of all, this beautiful, rhyming gift book gives you countless chances to articulate the promises grandmothers make in their hearts but often don't find opportunities to express to the grandchildren they adore -esteem-building promises like "I will always love you" and "I'll be your biggest fan!"
Nurture and celebrate your relationship with your beloved grandchild as together you read and re-read -- then joyfully live out --
a devoted grandma rabbit's fun-filled, love-inspired book of promises."

Photo Frames: Several styles to chose from, these will provide your mother with a constant reminder of her new grand baby! (various pricing)

Necklace, bracelet or other jewelry: Have these engraved, or find one with a beautiful saying or poem inside. This is something she can wear everyday if she chooses to remind her of the little one.

Blanket, Throw or Afghan: Grandma is going to need something to curl up with baby in when he/she stays the night and they read stories! How about a lovely Grandmother featured blanket-or similar-personalized or with a nice verse on it. I've added a few for you.

A Water Globe is a present that she can cherish for years. Things Remembered offers one for $34.99. Have a poem or just a date/name/etc.. engraved on it for extra special memories!

I know that whatever you decide upon will be cherished and loved!
Thanks and Happy Holidays! Session data

A great option if you have already has your little bundle of joy would be to make a custom photo book of your baby. 
There is a great website called http://www.picaboo.com and you can moke beautiful photo books there.