Tips to get started with elementary science, history, social studies
For elementary age kids, the library and videos are your best friend for science, history, geography, and all things factual!
These subjects can be learned in any order, at any level of interest. Let your child choose, or just sample from an array of engaging topics.
YouTube! Look online for project ideas.
Try MysteryScience.com or Generation Genius which have short videos on many topics.
Get picture books about cultures from around the globe.
Use big floor puzzles for geography, or use coloring books for maps
If you want some curriculum, it can help with ideas. Many people get a "spine" book as a jumping off point. Read a bit about things, then do some activities or watch some videos related to those ideas.
Science: Real Science Odyssey has excellent books for grades K-6, with their "Level 1" series. For a field science guide for outdoor explorers, try a Science Through Nature book.
History/Social Studies: Most people don't focus heavily on history with elementary aged kids, except to hit some highlights via historical fiction and picture books about times, places, and people. However if you want more of a guide, try Curiosity Chronicles, or the Early Times series by History Quest. For free lessons, try FishTank Learning (their ELA pages have Social Studies too).
For a more thorough list of resources, see the Curriculum Planning pages.