Old book series

Hannah was keeping an eye on her e-bay bids for some Judy Bolton books last night. She says that they are hard to find. I read a couple of Judy Bolton, but had other favorites. In first grade I read all of the Nancy Drew books and Bobbsey Twin books that I could find. By fourth grade I was hooked on Trixie Beldon, who I would have to say would be my choice to collect (but, of course, I already have the Bobbsey Twins.) Then it was Mandie books. They were gems. She and I started out the same age (12), but eventually my birthdays came faster than hers and I outgrew them. I also enjoyed the Grandma's Attic series. In high school my little brother started buying the "new" Hardy Boys casefiles and he would give them to me to read first (because he had an earlier bedtime and I would read them before mine, so he never really missed them anyway). Of course I loved the Little House books. (Click the link. It is a neat little website with quizzes on the Little House books, recipes, and my girls' favorite Little House storybooks.) And here's a funny for you. When I first read Anne of Green Gables as a girl, I remember finishing it and wishing that there was a sequel. It took me several years to find out that there were many sequels! I ended up liking L.M. Montgomery's Emily series even better, though. I think my favorite book of all, though was Heidi Grows Up, the second of the three Heidi books. So tell me, what were your favorite series of books as a child?