Mine is getting two scarves, earrings, a mug (posh bone china one) and diabetic chocolates from us. We are also spending a small fortune visiting her the weekend before Christmas, which requires train travel, staying in a hotel with our toddler, taking her out to lunch and paying for her taxi (long story, I could fill the Relationships board with tales of my MIL). We normally spend about £50 on her, same as other relatives on my side.
I think she likes it since I appeared on the scene some time ago now because I will often suggest things to DP that I think she'd like, or buy things I see for her if I travel for work, etc. Nothing expensive but things that are to her taste, and I think she does appreciate that.
DP tends to buy her stuff she asks for, such as books/DVDs; I buy stuff that I see that I think she'd like which she probably wouldn't buy for herself, even as a treat, and I get the impression she really likes to receive more "feminine" presents.
Our relationship is OK, probably because we only see each other twice a year. She drives DP, and me, bonkers but ultimately she is his mum and she brought up a lovely man all by herself, so I take deep breaths and remind myself of that when she gets going. 