Really REALLY good picture books, or a book of children's poems, something that has the potential to be cherished for years and maybe even kept into adulthood. I know in my family, almost all the toys eventually got tossed, but my favorite books, as well as those of both my parents, still grace the bookshelves. My boys (2 and 5) recently had birthdays and there was just Too Many Toys. They don't even really appreciate them when they get so much at once. And when they already have toys cluttering the place, it just makes it hard to find what they really want - they get overwhelmed, and they're always having to "clean up! clean up!" So, the last 4-5 birthday parties, I've been giving books - just books. But very carefully selected ones.
Another good idea (if it's not too pricy) is an annual membership to the Fernbank Museum, or the zoo, or a nearby nature center. That's something that the whole family can enjoy over and over. My in-laws gave my 5-year-old a session at summer camp for his birthday present, which we really couldn't afford at the time, so it was GREATLY appreciated. But it doesn't have to be that extravagant.
I like the idea of "experience" gifts, it can even be a one-time day trip or special outing, or some "classes" at Music Together or Little Gym, or just a special day with the grandparents all to herself (no siblings for a change). It's even better for the older kids, because they'll hold on to those memories (even if it isn't a trip to Disney World.)