With summer in full swing, lots of kids (and parents) are going online for ideas to keep busy. Common Sense has rounded up 30 unique things you and your kids can learn to do online (for free!) by a). watching a video, b). following instructions, or c). reading about a subject. Note: Many videos include an advertisement at the beginning, and some websites might link off to other topics or websites that might not be appropriate for your kids. We suggest previewing or watching along with your kids.