I would second the Magic School Bus series.
Also, Planet Earth is awesome.
This is probably too old (and possible too scary) for your DD, though I got it for the boys last Christmas when ds#3 was 3.5, but we've really enjoyed it:http://store.discovery.com/detail.ph...ects_dinosaurs
A friend's little boy really likes Dirty Jobs (we haven't seen it yet, but want to):http://store.discovery.com/?v=discov...ows_dirty-jobs
I remember checking out a series when ds#1 was 3.5-4, but I can't remember the name well enough to find it.
It was something like "How Things Are Made" or "How Things Are Done" or something. Now, when I search, I can only find the websites with similar names (like "How Stuff Works"). I think it may be because the "How it Works" part was a subtitle, and each video had it's own main title like "Hot Air Balloons" or "Electricity". I just know that he loved them, and then we moved and our current library doesn't carry much in the way of movies.