THATS MY MOM! CAN I GET A WHA WHAT?!?!?!!?!!!!! give her a card with your story on it. tell her a story of what you appreciate about her. I'm sure she would be ecstatic at a present like that. My mom and I grew up pretty damn poor. She knows whats on the inside is what truly matters.
I gift the various moms (three: mine, his and my step mom) with an 8x10 pic of something I think they'd like. His mom wants pics of him, so I take shots with him in it. My mom likes flowers. Step mom wanted to move to colorado, but didn't so she gets forest and mountain shots. It is fairly economical for me. two can't afford frames, so I provide dollar-store frames (since I'm pickier than they are, I find one that works for me and with the image) for all three, knowing stepmom will get what she wants. I told her long ago to feel free to keep, reframe or pass them on, no hurt feelings. She has given some to friends who really liked one or two.
When you mentioned this I realized that my mom's next will be her 50th also. I get my mom gift certificates that she can only spend on things she really likes. That way she has to treat herself to some new books or music or a show. I have to agree that a lovely picture of her kid or grandchild is an excellent idea. You could also somehow get your hands on a photo from the past that means a lot to her and do something with it. My cousin went through my grandparents' old photos, copied them, and organized them to make several well-put-together photo albums for her mom and others from her mother's generation. It was one of the prettiest things I have ever seen. I have seen beautiful things done with collages made of personal photos. This is pretty low budget and requires a lot of personal thought, which makes it personal and meaningful. Maybe it could have photos of her and people in the family.
I like bubblebath, incense, candles, nature sound cds... Any sort of personal relaxation items... Being a single mom, I would have to give my kids the money to buy me something (they don't get an allowance or anything)... So that kinda takes the joy out of it... LOL I would much rather put that money into their gifts. Watching their eyes light up when they see that I've given them something that they really want, is a gift in itself...