PBS Kids - Sid the Science Kid

 Sid the Science Kid  is a television show on PBS geared towards preschool and kindergarten.  (But I think 1st and 2nd graders would like it, too!)   Every episode follows the scientific method.  Sid starts every episode with a question he is wondering about.  He takes his question to school and he and his classmates investigate and explore the concept.  His teacher, Miss Susie, then explains the concept (usually through song) and real world connections.  When Sid returns home, he tells his grandma and parents what he learned.  At bedtime, he reflects on what he learned about science today.

They don't have full episodes online but here are many songs and investigations played in Flash to go along with science content.   There are songs and investigations on tools & measurement, transformations of matter, senses, health, simple machines, backyard science, human body, and weather.